Form DEFM14A Oaktree Strategic Income

OAKTREE SPECIALTY LENDING CORPORATION

333 South Grand Avenue, 28th Floor

Los Angeles, CA 90071

MERGER PROPOSED — YOUR VOTE IS VERY IMPORTANT

November 30, 2022

Dear Stockholder:

You are cordially invited to attend the 2023 Annual Meeting of Stockholders (the “OCSL Annual Meeting”) of Oaktree Specialty Lending Corporation, a Delaware corporation (“OCSL”), to be held virtually on January 20, 2023, at 10:00 a.m., Pacific Time (1:00 p.m. Eastern Time), at the following website: www.virtualshareholdermeeting.com/OCSL2023. Stockholders of record of OCSL at the close of business on November 28, 2022 are entitled to notice of, and to vote at, the OCSL Annual Meeting or any adjournment or postponement thereof.

The notice of annual meeting and the joint proxy statement/prospectus accompanying this letter provide an outline of the business to be conducted at the OCSL Annual Meeting. At the OCSL Annual Meeting, you will be asked to:

Closing of the Mergers (as defined below) is contingent upon (a) OCSL stockholder approval of the Merger Stock Issuance Proposal, (b) OSI2 stockholder approval of the Merger Agreement and (c) satisfaction or waiver of certain other closing conditions. If the Mergers do not close, then the OCSL Common Stock will not be issued pursuant to the Merger Stock Issuance Proposal, even if approved by the OCSL stockholders.

OCSL and OSI2 are proposing a combination of both companies by a merger and related transactions pursuant to the Merger Agreement in which Merger Sub would merge with and into OSI2 (the “Merger”), with OSI2 continuing as the surviving company and as a wholly-owned subsidiary of OCSL. Immediately after the effectiveness of the Merger, OSI2 will merge with and into OCSL (together with the Merger, the “Mergers”), with OCSL continuing as the surviving company.

Subject to the terms and conditions of the Merger Agreement, at the effective time of the Merger (the “Effective Time”), each share of common stock, par value $0.001 per share, of OSI2 (“OSI2 Common Stock”) issued and outstanding immediately prior to the Effective Time (other than shares owned by OCSL or any of its consolidated subsidiaries (the “Cancelled Shares”)) will be converted into the right to receive a number of shares

of OCSL Common Stock equal to the Exchange Ratio (as defined below), plus any cash in lieu of fractional shares.

Under the Merger Agreement, as of a mutually agreed date no earlier than 48 hours (excluding Sundays and holidays) prior to the Effective Time (such date, the “Determination Date”), each of OSI2 and OCSL will deliver to the other a calculation of its net asset value as of such date (such calculation with respect to OSI2, the “Closing OSI2 Net Asset Value” and such calculation with respect to OCSL, the “Closing OCSL Net Asset Value”), in each case based on the same assumptions and methodologies, and applying the same categories of adjustments to net asset value (except as may be mutually agreed by the parties), historically used in preparing the calculation of the net asset value per share by the applicable party. Based on such calculations, the parties will calculate the “OSI2 Per Share NAV”, which will be equal to (i) the Closing OSI2 Net Asset Value divided by (ii) the number of shares of OSI2 Common Stock issued and outstanding as of the Determination Date (excluding any Cancelled Shares), and the “OCSL Per Share NAV”, which will be equal to (A) the Closing OCSL Net Asset Value divided by (B) the number of shares of OCSL Common Stock issued and outstanding as of the Determination Date. The “Exchange Ratio” will be equal to the quotient (rounded to four decimal places) of (i) the OSI2 Per Share NAV divided by (ii) the OCSL Per Share NAV.

In connection with entry into the Merger Agreement and subject to completion of the transactions contemplated thereby, Oaktree Fund Advisors, LLC has agreed to waive $9.0 million of base management fees payable to it by OCSL as follows: $6.0 million at a rate of $1.5 million per quarter (with such amount appropriately prorated for any partial quarter) in the first year following closing of the Mergers and $3.0 million at a rate of $750,000 per quarter (with such amount appropriately prorated for any partial quarter) in the second year following closing of the Mergers.

Your vote is extremely important. The holders of at least a majority of the issued and outstanding shares of OCSL Common Stock must be present at the OCSL Annual Meeting for each of the OCSL Proposals to be voted on. The election of directors in connection with the Director Proposal requires the affirmative vote of the holders of at least a plurality of votes cast by holders of shares of OCSL Common Stock present at the OCSL Annual Meeting, virtually or represented by proxy, and entitled to vote thereat. The approval of each of the Auditor Proposal and the Merger Stock Issuance Proposal requires the affirmative vote of the holders of at least a majority of votes cast by holders of shares of OCSL Common Stock present at the OCSL Annual Meeting, virtually or represented by proxy, and entitled to vote thereat. The approval of the Reverse Stock Split Proposal requires the affirmative vote of the holders of a majority of the outstanding shares of OCSL Common Stock. Votes to “withhold authority” and broker non-votes (which occur when a beneficial owner does not instruct its broker, bank, trustee or nominee holding its shares of OCSL Common Stock how to vote such shares on its behalf), if any, will not be included in determining the number of votes cast and, as a result, will have no effect on the voting outcome of the Director Proposal. Abstentions and broker non-votes, if any, will not be included in determining the number of votes cast and, as a result, will have no effect on the voting outcome of the Auditor Proposal and the Merger Stock Issuance Proposal. Abstentions and broker non-votes, if any, will have the effect of a vote against the Reverse Stock Split Proposal. For the OCSL Annual Meeting, broker non-votes, if any, will be treated as shares present for quorum purposes.

After careful consideration and, with respect to the Merger Stock Issuance Proposal, on the recommendation of a special committee of the Board of Directors of OCSL (the “OCSL Board”) comprised entirely of certain independent directors, the OCSL Board unanimously recommends that OCSL’s stockholders vote “FOR” the election of each of the nominees proposed by the OCSL Board in connection with the Director Proposal, “FOR” the Auditor Proposal, “FOR” the Merger Stock Issuance Proposal and “FOR” the Reverse Stock Split Proposal.

It is important that your shares be represented at the OCSL Annual Meeting. Please follow the instructions on the enclosed proxy card and vote via the Internet, by telephone or by signing, dating and returning the enclosed proxy card. OCSL encourages you to vote via the Internet as it saves OCSL significant time and processing costs. Voting by proxy does not deprive you of your right to participate in the OCSL Annual Meeting.

This joint proxy statement/prospectus describes the OCSL Annual Meeting, the Mergers and the documents related to the Mergers (including the Merger Agreement) that OCSL’s stockholders should review before voting on the Merger Stock Issuance Proposal and should be retained for future reference. Please carefully read this entire document, including “Risk Factors” beginning on page 23 and as otherwise incorporated by reference in this joint proxy statement/prospectus, for a discussion of the risks relating to the Mergers and OCSL. OCSL files periodic reports, current reports, proxy statements and other information with the U.S. Securities and Exchange Commission. This information is available free of charge, and stockholder inquiries can be made, by contacting OCSL at 333 South Grand Ave., 28th Floor, Los Angeles, CA 90071 or by calling OCSL collect at (213) 830-6300 or on OCSL’s website at www.oaktreespecialtylending.com. The Securities and Exchange Commission also maintains a website at www.sec.gov that contains such information. Except for the documents incorporated by reference into this joint proxy statement/prospectus, information on OCSL’s website is not incorporated into or a part of this joint proxy statement/prospectus.

No matter how many or few shares in OCSL you own, your vote and participation are very important to us.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of the shares of OCSL Common Stock to be issued under this joint proxy statement/prospectus or determined if this joint proxy statement/prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This joint proxy statement/prospectus is dated November 30, 2022 and is first being mailed or otherwise delivered to OCSL stockholders on or about December 1, 2022.

OAKTREE SPECIALTY LENDING CORPORATION

333 South Grand Avenue, 28th Floor

Los Angeles, CA 90071

NOTICE OF VIRTUAL 2023 ANNUAL MEETING OF STOCKHOLDERS

Online Meeting Only — No Physical Meeting Location

www.virtualshareholdermeeting.com/OCSL2023

January 20, 2023, 10:00 a.m., Pacific Time (1:00 p.m., Eastern Time)

Dear Stockholders:

The 2023 Annual Meeting of Stockholders (the “OCSL Annual Meeting”) of Oaktree Specialty Lending Corporation, a Delaware corporation (“OCSL”), will be conducted online on January 20, 2023, at 10:00 a.m., Pacific Time (1:00 p.m., Eastern Time) at the following website: www.virtualshareholdermeeting.com/OCSL2023.

At the OCSL Annual Meeting, in addition to transacting such other business as may properly come before the meeting and any adjournments and postponements thereof, the OCSL stockholders will consider and vote on the following proposals as to OCSL:

AFTER CAREFUL CONSIDERATION AND, WITH RESPECT TO THE MERGER STOCK ISSUANCE PROPOSAL, ON THE RECOMMENDATION OF A SPECIAL COMMITTEE OF THE BOARD OF DIRECTORS OF OCSL (THE “OCSL BOARD”) COMPRISED ENTIRELY OF CERTAIN INDEPENDENT DIRECTORS, THE OCSL BOARD UNANIMOUSLY RECOMMENDS THAT OCSL’S STOCKHOLDERS VOTE “FOR” THE ELECTION OF EACH OF THE NOMINEES PROPOSED BY THE OCSL BOARD IN CONNECTION WITH THE DIRECTOR PROPOSAL, “FOR” THE AUDITOR PROPOSAL, “FOR” THE MERGER STOCK ISSUANCE PROPOSAL AND “FOR” THE REVERSE STOCK SPLIT PROPOSAL.

You have the right to receive notice of, and to vote at, the OCSL Annual Meeting if you were a stockholder of record of OCSL at the close of business on November 28, 2022. A joint proxy statement/prospectus is attached to this Notice that describes the matters to be voted upon at the OCSL Annual Meeting or any adjournment(s) or postponement(s) thereof. The enclosed proxy card will instruct you as to how you may vote your proxy via the Internet, by telephone or by signing, dating and returning the enclosed proxy card. In addition, information regarding how to find the logistical details of the OCSL Annual Meeting (including how to remotely access, participate in and vote during the virtual meeting) is included beginning on page 2 of the attached joint proxy statement/prospectus.

Whether or not you plan to participate in the OCSL Annual Meeting, we encourage you to vote your shares by following the instructions on the enclosed proxy card. Please note, however, that if you wish to vote during the OCSL Annual Meeting and your shares are held of record by a broker, bank, trustee or nominee, you must obtain a “legal” proxy issued in your name from that record holder.

We are not aware of any other business, or any other nominees for election as directors of OCSL, that may properly be brought before the OCSL Annual Meeting.

Thank you for your continued support of OCSL.

Los Angeles, CA

November 30, 2022

To ensure proper representation at the OCSL Annual Meeting, please follow the instructions on the enclosed proxy card to vote your shares via the Internet or telephone, or by signing, dating and returning the enclosed proxy card. Even if you vote your shares prior to the OCSL Annual Meeting, you still may participate in the OCSL Annual Meeting.

OAKTREE STRATEGIC INCOME II, INC.

333 South Grand Avenue, 28th Floor

Los Angeles, CA 90071

MERGER PROPOSED — YOUR VOTE IS VERY IMPORTANT

November 30, 2022

Dear Stockholder:

You are cordially invited to attend the Special Meeting of Stockholders (the “OSI2 Special Meeting”) of Oaktree Strategic Income II, Inc., a Delaware corporation (“OSI2”), to be held virtually on January 20, 2023, at 10:30 a.m., Pacific Time (1:30 p.m. Eastern Time), at the following website: www.virtualshareholdermeeting.com/OSI22023SM. Stockholders of record of OSI2 at the close of business on November 28, 2022 are entitled to notice of, and to vote at, the OSI2 Special Meeting or any adjournment or postponement thereof.

The notice of special meeting and the joint proxy statement/prospectus accompanying this letter provide an outline of the business to be conducted at the OSI2 Special Meeting. At the OSI2 Special Meeting, you will be asked to adopt the Agreement and Plan of Merger, dated as of September 14, 2022 (the “Merger Agreement”), among OSI2, Oaktree Specialty Lending Corporation, a Delaware corporation (“OCSL”), Project Superior Merger Sub, Inc., a Delaware corporation and a direct wholly-owned subsidiary of OCSL (“Merger Sub”), and, for the limited purposes set forth therein, Oaktree Fund Advisors, LLC, a Delaware limited liability company and investment adviser to each of OCSL and OSI2, and approve the transactions contemplated thereby, including the Mergers (as defined below) (such proposal collectively, the “Merger Proposal”).

Closing of the Mergers (as defined below) is contingent upon (i) OSI2 stockholder approval of the Merger Proposal, (ii) OCSL stockholder approval of the issuance of shares of common stock, par value $0.01 per share, of OCSL (“OCSL Common Stock”) in connection with the Merger Agreement and (iii) satisfaction or waiver of certain other closing conditions.

OCSL and OSI2 are proposing a combination of both companies by a merger and related transactions pursuant to the Merger Agreement in which Merger Sub would merge with and into OSI2 (the “Merger”), with OSI2 continuing as the surviving company and as a wholly owned subsidiary of OCSL. Immediately after the effectiveness of the Merger, OSI2 will merge with and into OCSL (together with the Merger, the “Mergers”), with OCSL continuing as the surviving company.

Subject to the terms and conditions of the Merger Agreement, at the effective time of the Merger (the “Effective Time”), each share of common stock, par value $0.001 per share, of OSI2 (“OSI2 Common Stock”) issued and outstanding immediately prior to the Effective Time (other than shares owned by OCSL or any of its consolidated subsidiaries, the “Cancelled Shares”)) will be converted into the right to receive a number of shares of OCSL Common Stock equal to the Exchange Ratio (as defined below), plus any cash in lieu of fractional shares.

Under the Merger Agreement, as of a mutually agreed date no earlier than 48 hours (excluding Sundays and holidays) prior to the Effective Time (such date, the “Determination Date”), each of OSI2 and OCSL will deliver to the other a calculation of its net asset value as of such date (such calculation with respect to OSI2, the “Closing OSI2 Net Asset Value” and such calculation with respect to OCSL, the “Closing OCSL Net Asset Value”), in each case based on the same assumptions and methodologies, and applying the same categories of adjustments to net asset value (except as may be mutually agreed by the parties), historically used in preparing the calculation of the net asset value per share by the applicable party. Based on such calculations, the parties will calculate the “OSI2 Per Share NAV”, which will be equal to (i) the Closing OSI2 Net Asset Value divided by (ii) the number

of shares of OSI2 Common Stock issued and outstanding as of the Determination Date (excluding any Cancelled Shares), and the “OCSL Per Share NAV”, which will be equal to (A) the Closing OCSL Net Asset Value divided by (B) the number of shares of OCSL Common Stock issued and outstanding as of the Determination Date. The “Exchange Ratio” will be equal to the quotient (rounded to four decimal places) of (i) the OSI2 Per Share NAV divided by (ii) the OCSL Per Share NAV.

The market value of the consideration to be received by OSI2’s stockholders will fluctuate with changes in the market price of OCSL Common Stock. OSI2 urges you to obtain current market quotations of OCSL Common Stock. OCSL Common Stock trades on the Nasdaq Global Select Market (“Nasdaq”) under the ticker symbol “OCSL”. The following table shows the closing sale prices of OCSL Common Stock, as reported on Nasdaq on September 13, 2022, the last trading day before the execution of the Merger Agreement, and on November 29, 2022, the last trading day before printing this document.

Your vote is extremely important. At the OSI2 Special Meeting, you will be asked to vote on the Merger Proposal. The approval of the Merger Proposal requires the affirmative vote of the holders of a majority of the outstanding shares of OSI2 Common Stock. Abstentions and broker non-votes (which occur when a beneficial owner does not instruct its broker, bank, trustee or nominee holding its shares of OSI2 Common Stock how to vote such shares on its behalf) will not count as affirmative votes cast and will therefore have the same effect as votes “against” the Merger Proposal.

After careful consideration, on the recommendation of a special committee of the Board of Directors of OSI2, comprised solely of certain independent directors, the Board of Directors of OSI2 unanimously approved the Merger Agreement and the transactions contemplated thereby, including the Mergers, and unanimously recommends that OSI2’s stockholders vote “FOR” the Merger Proposal.

It is important that your shares be represented at the OSI2 Special Meeting. Please follow the instructions on the enclosed proxy card and vote via the Internet or by telephone. OSI2 encourages you to vote via the Internet as it saves OSI2 significant time and processing costs. However, you may also vote your proxy by signing, dating and returning the enclosed proxy card to OSI2 in the postage-paid envelope provided. Voting by proxy does not deprive you of your right to participate in the OSI2 Special Meeting.

This joint proxy statement/prospectus describes the OSI2 Special Meeting, the Mergers and the documents related to the Mergers (including the Merger Agreement) that OSI2’s stockholders should review before voting on the Merger Proposal and should be retained for future reference. Please carefully read this entire document, including “Risk Factors ” beginning on page 23 and as otherwise incorporated by reference in this joint proxy statement/prospectus, for a discussion of the risks relating to the Mergers, OCSL and OSI2. OSI2 files periodic reports, current reports, proxy statements and other information with the U.S. Securities and Exchange Commission. This information is available free of charge, and stockholder inquiries can be made, by contacting OSI2 at 333 South Grand Ave., 28th Floor, Los Angeles, CA 90071 or by calling OSI2 collect at (213) 830-6300. The Securities and Exchange Commission also maintains a website at www.sec.gov that contains such information. No matter how many or few shares in OSI2 you own, your vote and participation are very important to us.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of the shares of OCSL Common Stock to be issued under this joint proxy statement/prospectus or determined if this joint proxy statement/prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This joint proxy statement/prospectus is dated November 30, 2022 and is first being mailed or otherwise delivered to OSI2 stockholders on or about December 1, 2022.

OAKTREE STRATEGIC INCOME II, INC.

333 South Grand Avenue, 28th

Floor Los Angeles, CA 90071

NOTICE OF VIRTUAL SPECIAL MEETING OF STOCKHOLDERS

Online Meeting Only — No Physical Meeting Location

www.virtualshareholdermeeting.com/OSI22023SM

January 20, 2023, 10:30 a.m., Pacific Time (1:30 p.m., Eastern Time)

Dear Stockholders:

The Special Meeting of Stockholders (the “OSI2 Special Meeting”) of Oaktree Strategic Income II, Inc., a Delaware corporation (“OSI2”), will be conducted online on January 20, 2023, at 10:30 a.m., Pacific Time (1:30 p.m., Eastern Time), at the following website: www.virtualshareholdermeeting.com/OSI22023SM.

At the OSI2 Special Meeting, in addition to transacting such other business as may properly come before the meeting and any adjournments and postponements thereof, stockholders of OSI2 will consider and vote on a proposal to adopt the Agreement and Plan of Merger, dated as of September 14, 2022 (the “Merger Agreement”), among OSI2, Oaktree Specialty Lending Corporation, a Delaware corporation (“OCSL”), Project Superior Merger Sub, Inc., a Delaware corporation and a direct wholly-owned subsidiary of OCSL (“Merger Sub”), and, for the limited purposes set forth therein, Oaktree Fund Advisors, LLC, a Delaware limited liability company and investment adviser to each of OCSL and OSI2, and approve the transactions contemplated thereby, including the Mergers (as defined below) (such proposal collectively, the “Merger Proposal”).

OSI2 is proposing a combination of OCSL and OSI2 by a merger and related transactions pursuant to the Merger Agreement in which Merger Sub would merge with and into OSI2 (the “Merger”), with OSI2 continuing as the surviving company and as a wholly owned subsidiary of OCSL. Immediately after the effectiveness of the Merger, OSI2 will merge with and into OCSL (together with the Merger, the “Mergers”), with OCSL continuing as the surviving company.

AFTER CAREFUL CONSIDERATION, ON THE RECOMMENDATION OF A SPECIAL COMMITTEE OF THE BOARD OF DIRECTORS OF OSI2, COMPRISED SOLELY OF CERTAIN INDEPENDENT DIRECTORS, THE BOARD OF DIRECTORS OF OSI2 UNANIMOUSLY APPROVED THE MERGER AGREEMENT AND THE TRANSACTIONS CONTEMPLATED THEREBY, INCLUDING THE MERGERS, AND UNANIMOUSLY RECOMMENDS THAT OSI2’S STOCKHOLDERS VOTE “FOR” THE MERGER PROPOSAL.

You have the right to receive notice of, and to vote at, the OSI2 Special Meeting if you were a stockholder of record of OSI2 at the close of business on November 28, 2022. A joint proxy statement/prospectus is attached to this Notice that describes the matters to be voted upon at the OSI2 Special Meeting or any adjournment(s) or postponement(s) thereof. The enclosed proxy card will instruct you as to how you may vote your proxy via the Internet, by telephone or by signing, dating and returning the enclosed proxy card. In addition, information regarding how to find the logistical details of the OSI2 Special Meeting (including how to remotely access, participate in and vote during the virtual meeting) is included on page 3 of the attached joint proxy statement/prospectus.

Whether or not you plan to participate in the OSI2 Special Meeting, we encourage you to vote your shares by following the instructions on the enclosed proxy card. Please note, however, that if you wish to vote during the OSI2 Special Meeting and your shares are held of record by a broker, bank, trustee or nominee, you must obtain a “legal” proxy issued in your name from that record holder.

We are not aware of any other business that may properly be brought before the OSI2 Special Meeting.

Thank you for your continued support of OSI2.

Los Angeles, CA

November 30, 2022

To ensure proper representation at the OSI2 Special Meeting, please follow the instructions on the enclosed proxy card to vote your shares via the Internet or telephone, or by signing, dating and returning the enclosed proxy card. Even if you vote your shares prior to the OSI2 Special Meeting, you still may participate in the OSI2 Special Meeting.

TABLE OF CONTENTS

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ABOUT THIS DOCUMENT

This document, which forms part of a registration statement on Form N-14 filed with the U.S. Securities and Exchange Commission (the “SEC”) by OCSL (File No. 333-267988), constitutes a prospectus of OCSL under Section 5 of the Securities Act of 1933, as amended (the “Securities Act”), with respect to the shares of OCSL Common Stock to be issued to OSI2 Stockholders pursuant to the Merger Agreement.

This document also constitutes a joint proxy statement of OCSL and OSI2 under Section 14(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). It also constitutes a notice of meeting with respect to: (1) the Annual Meeting of Stockholders of OCSL (the “OCSL Annual Meeting”), at which OCSL Stockholders will be asked to vote upon the Director Proposal (as defined below), the Auditor Proposal (as defined below), the Merger Stock Issuance Proposal (as defined below) and the Reverse Stock Split Proposal (as defined below); and (2) the Special Meeting of Stockholders of OSI2 (the “OSI2 Special Meeting”), at which OSI2 Stockholders will be asked to vote upon the Merger Proposal (as defined below).

You should rely only on the information contained in this joint proxy statement/prospectus, including in determining how to vote the shares of OCSL Common Stock or OSI2 Common Stock, as applicable. No one has been authorized to provide you with information that is different from that contained in this joint proxy statement/prospectus. This joint proxy statement/prospectus is dated November 30, 2022. You should not assume that the information contained in this joint proxy statement/prospectus is accurate as of any date other than that date. Neither any mailing of this joint proxy statement/prospectus to OCSL Stockholders or OSI2 Stockholders nor the issuance of OCSL Common Stock in connection with the Mergers will create any implication to the contrary.

This joint proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction.

Except where the context otherwise indicates, information contained in this joint proxy statement/prospectus regarding OCSL has been provided by OCSL and information contained in this joint proxy statement/prospectus regarding OSI2 has been provided by OSI2.

When used in this document, unless otherwise indicated in this document or the context otherwise requires:

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Financial information of OSI2 as of or for the year ended September 30, 2022 presented in this joint proxy statement/prospectus is subject to the completion of OSI2’s financial closing procedures and is not a comprehensive statement of OSI2’s financial position, results of operations or cash flows as of or for the year ended September 30, 2022. Final results may differ materially as a result of the completion of OSI2’s financial closing procedures, as well as any subsequent events, including the discovery of information affecting fair values of OSI2’s portfolio investments as of September 30, 2022, arising between the date of this joint proxy statement/prospectus and the completion of OSI2’s financial statements and the filing of OSI2’s annual report on Form 10-K for the year then ended.

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Such select financial information of OSI2 provided in this joint proxy statement/prospectus has been prepared by, and is the responsibility of OSI2 management. Ernst & Young LLP, OSI2’s independent registered public accounting firm, has not audited, reviewed, compiled, or performed any procedures with respect to the OSI2 select financial information. Accordingly, Ernst & Young LLP does not express an opinion or any other form of assurance with respect thereto.

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QUESTIONS AND ANSWERS ABOUT THE STOCKHOLDER MEETINGS AND THE PROPOSALS

The questions and answers below highlight only selected information from this joint proxy statement/prospectus. They do not contain all of the information that may be important to you. You should read carefully this entire document to fully understand the Merger Agreement and the transactions contemplated thereby (including the Mergers) and the proposals to be presented at and the voting procedures for each of the OCSL Annual Meeting and the OSI2 Special Meeting.

Questions and Answers about the Stockholder Meetings

OSI2 is furnishing these materials in connection with the solicitation of proxies by the OSI2 Board for use at the OSI2 Special Meeting to be held virtually on January 20, 2023, at 10:30 a.m., Pacific Time (1:30 p.m. Eastern Time), at the following website: www.virtualshareholdermeeting.com/OSI22023SM.

This joint proxy statement/prospectus and the accompanying materials are being mailed on or about December 1, 2022 to stockholders of record of OCSL and OSI2 described below and are available at www.proxyvote.com.

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An OCSL Stockholder may also authorize a proxy by telephone or through the Internet using the toll-free telephone numbers or web address printed on your proxy card. Authorizing a proxy by telephone or through the Internet requires you to input the control number located on your proxy card. After inputting the control

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number, you will be prompted to direct your proxy to vote on each proposal. You will have an opportunity to review your directions and make any necessary changes before submitting your directions and terminating the telephone call or Internet link.

Important notice regarding the availability of proxy materials for the OCSL Annual Meeting. OCSL’s joint proxy statement/prospectus, OCSL’s Annual Report on Form 10-K for the year ended September 30, 2022 and the proxy card are available at www.proxyvote.com.

An OSI2 Stockholder may also authorize a proxy by telephone or through the Internet using the toll-free telephone numbers or web address printed on your proxy card. Authorizing a proxy by telephone or through the Internet requires you to input the control number located on your proxy card. After inputting the control number, you will be prompted to direct your proxy to vote on each proposal. You will have an opportunity to review your directions and make any necessary changes before submitting your directions and terminating the telephone call or Internet link.

Important notice regarding the availability of proxy materials for the OSI2 Special Meeting. OSI2’s joint proxy statement/prospectus and the proxy card are available at www.proxyvote.com.

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Shares for which brokers have not received voting instructions from the beneficial owner of the shares and do not have discretionary authority to vote on certain proposals are considered “broker non-votes” with respect to such proposals.

For the OCSL Annual Meeting, broker non-votes, if any, will be treated as shares present for quorum purposes. Such broker non-votes will not be included in determining the number of votes cast and, as a result, will have no effect on the Director Proposal, the Auditor Proposal or the Merger Stock Issuance Proposal. Since the Reverse Stock Split Proposal requires the affirmative vote of a majority of the outstanding shares of OCSL Common Stock and broker non-votes will not be counted as affirmative votes, broker non-votes will have the same effect as votes “against” the Reverse Stock Split Proposal.

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For the OSI2 Special Meeting, because the sole proposal is a matter on which brokers do not have discretionary authority to vote, OSI2 does not expect any broker non-votes. However, if shares representing broker non-votes are presented at the OSI2 Special Meeting, such shares will not be treated as shares present for quorum purposes and will not count as affirmative votes cast and will therefore have the same effect as votes “against” the Merger Proposal.

Pursuant to OCSL’s fourth amended and restated bylaws (“OCSL’s bylaws”), the chairman of the OCSL Annual Meeting will have the power to adjourn the OCSL Annual Meeting, whether or not a quorum is present, from time to time for any reason and without notice other than announcement at the OCSL Annual Meeting.

Pursuant to OSI2’s amended and restated bylaws (“OSI2’s bylaws”), if less than a quorum is present at the OSI2 Special Meeting or if an insufficient number of votes is present for the adoption of the Merger Proposal at such meeting, the chairman of the OSI2 Special Meeting or OSI2 stockholders holding a majority of the shares of OSI2 Common Stock will have the power to adjourn the OSI2 Special Meeting from time to time without notice other than announcement at the OSI2 Special Meeting.

The affirmative vote of the holders of a majority of the votes cast by the holders of outstanding shares of OCSL Common Stock at the OCSL Annual Meeting in person or by proxy at a meeting at which a quorum is present is required for approval of the Auditor Proposal and the Merger Stock Issuance Proposal (i.e., the number of shares voted “for” the proposal must exceed the number of shares voted “against” such proposal). The approval of the Reverse Stock Split Proposal requires the affirmative vote of a majority of the outstanding shares of OCSL Common Stock. Abstentions and broker non-votes, if any, will not be included in determining the number of votes cast and, as a result, will have no effect on the Auditor Proposal or the Merger Stock Issuance Proposal. Abstentions and broker non-votes, if any, will have the effect of a vote “against” the Reverse Stock Split Proposal.

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Q: What vote is required to approve the proposal being considered at the OSI2 Special Meeting?

If the Mergers do not close because either the OCSL Stockholders or the OSI2 Stockholders do not approve the Merger Stock Issuance Proposal or Merger Proposal, as applicable, or any of the other conditions to the Closing is not satisfied or waived, each of OCSL and OSI2 will continue to operate pursuant to the current agreements in place for each, and each of OCSL’s and OSI2’s respective directors and officers will continue to serve as its directors and officers, respectively, until their successors are duly elected and qualified, or their earlier death, removal or resignation.

The registration statement (of which this joint proxy statement/prospectus forms a part), the Notice of Annual Meeting of Stockholders of OCSL, the Notice of Special Meeting of Stockholders of OSI2 and the proxy cards are available at www.proxyvote.com.

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Investor Relations

Oaktree Specialty Lending Corporation

1301 Avenue of the Americas, 34th Floor

New York, NY 10019

(212) 284-1900

[email protected]

If you are an OSI2 Stockholder, you can contact OSI2 by calling collect at (213) 830-6300, by e-mail to OSI2 at [email protected], or by writing to OSI2 at the below contact information with any additional questions:

Oaktree Strategic Income II, Inc.

333 South Grand Avenue, 28th Floor

Attention: Mary Gallegly

Los Angeles, CA 90071

(213) 830-6300

Questions and Answers about the Mergers

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OSI2 and OCSL will update and redeliver the Closing OSI2 Net Asset Value or the Closing OCSL Net Asset Value, respectively, in the event of a material change to such calculation between the Determination Date and the closing of the Mergers (including for any dividend declared by either OSI2 or OCSL after the Determination Date but prior to the closing of the Mergers) and if needed to ensure that the calculation is determined within 48 hours (excluding Sundays and holidays) prior to the Effective Time.

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Following the Effective Time, the holders of shares of OSI2 Common Stock will be entitled to receive dividends or other distributions declared by the OCSL Board with a record date after the Effective Time theretofore payable with respect to the whole shares of OCSL Common Stock received as part of the Merger Consideration.

OSI2’s investment objective is to generate current income and long-term capital appreciation. OSI2 seeks to achieve its investment objective without subjecting principal to undue risk of loss by lending to and investing in the debt of public and private companies, primarily in situations where a company or its owners are (a) overleveraged or facing pressures to recapitalize, (b) unable to access broadly syndicated capital markets, (c) undervalued after having recently exited bankruptcy, completed a restructuring or are in a cyclically out-of-favor industry or (d) otherwise affected by mispricings or inefficiencies in the capital markets or at different points throughout the credit cycle.

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Oaktree is generally focused on middle-market companies, which OCSL and OSI2 define as companies with enterprise values of between $100 million and $750 million. Each of OCSL and OSI2 generally invests in securities that are rated below investment grade by rating agencies or that would be rated below investment grade if they were rated. Below investment grade securities, which are often referred to as “high yield” and “junk,” have predominantly speculative characteristics with respect to the issuer’s capacity to pay interest and repay principal.

As of September 30, 2022, 97% of OSI2’s portfolio investments are also in OCSL’s portfolio as OSI2 has been co-investing with OCSL and other Oaktree entities since its inception. As a result, OCSL and OSI2 have substantially similar risks as each focuses on making investments in privately-held middle-market companies.

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However, under the OCSL Investment Advisory Agreement (which will serve as the investment advisory agreement for the combined company post-Mergers), the base management fee is calculated at a rate of 1.50% of OCSL’s total gross assets at the end of each quarter, including any investment made with borrowings, but excluding cash and cash equivalents; provided, however, the base management fee is calculated at an annual rate of 1.00% of the value of OCSL’s total gross assets, including any investments made with borrowings, but excluding cash and cash equivalents, that exceeds the product of (i) 200% (calculated in accordance with the Investment Company Act, and giving effect to exemptive relief OCSL has received with respect to debentures issued by a small business investment company subsidiary) and (ii) OCSL’s net assets. While Oaktree has agreed to waive $9.0 million of base management fees payable to it ($6.0 million at a rate of $1.5 million per quarter (with such amount appropriately prorated for any partial quarter) in the first year following closing of the Mergers and $3.0 million at a rate of $750,000 per quarter (with such amount appropriately prorated for any partial quarter) in the second year following the closing of the Mergers), OCSL’s base management fee rate is higher than that currently paid by OSI2 although it is equivalent to the OSI2 base management fee rate following a Qualified Listing. Such higher base management fee and higher acquired fund fees could result in decreases in net investment income or dividends.

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RISK FACTORS

In addition to the other information included in this document, you should carefully consider the risks described below in determining whether to approve (i) in the case of OCSL Stockholders, the Merger Stock Issuance Proposal and (ii)  in the case of OSI2 Stockholders, the Merger Proposal. The information in “Item 1A. Risk Factors” in Part I of OCSL’s Annual Report on Form  10-K (File No. 814-00755) for the fiscal year ended September 30, 2022. The information in “Item 1A. Risk Factors” in Part I of OSI2’s Annual Report on Form 10-K (File No. 814-01281) for the fiscal year ended September 30, 2022 and in Part II, Item 1A of OSI2’s  Quarterly Report for the period ended June 30, 2022 is incorporated herein by reference for general risks related to OSI2. The occurrence of any of these risks could materially and adversely affect the business, prospects, financial condition, results of operations and cash flow of OCSL and OSI2 and, following the Mergers, the combined company and might cause you to lose all or part of your investment. The risks, as set out below and incorporated by reference herein, are not the only risks OCSL and OSI2 and, following the Mergers, the combined company face, and there may be additional risks that OCSL and OSI2 do not presently know of or that they currently consider not likely to have a significant impact. New risks may emerge at any time and OCSL and OSI2 cannot predict such risks or estimate the extent to which they may affect the business or financial performance of OCSL and OSI2 and, following the Mergers, the combined company. See also “Incorporation by Reference for OCSL,” “Incorporation by Reference for OSI2” and “Where You Can Find More Information” in this joint proxy statement/prospectus.

Risks Relating to the Mergers

Because the trading price of OCSL Common Stock and the NAV per share of OSI2 Common Stock and OCSL Common Stock will fluctuate, OSI2 Stockholders cannot be sure of the market value of the consideration they will receive in connection with the Mergers until the closing date of the Mergers.

At the Effective Time, each share of OSI2 Common Stock issued and outstanding immediately prior to the Effective Time (other than Cancelled Shares) will be converted into the right to receive a number of shares of OCSL Common Stock, equal to the Exchange Ratio, plus any cash (without interest) in lieu of fractional shares. The market value of such consideration to be received by OSI2 Stockholders upon completion of the Mergers (the “Merger Consideration”) may vary from the closing price of OCSL Common Stock on the date prior to announcement of the Mergers, on the date of the OSI2 Special Meeting and on the date the Mergers are completed. Any change in the market price of OCSL Common Stock prior to completion of the Mergers will affect the market value of the Merger Consideration that OSI2 Stockholders will receive upon completion of the Mergers. Additionally, the Exchange Ratio will fluctuate as OSI2’s and OCSL’s respective NAVs change prior to Closing.

Accordingly, at the time of the OSI2 Special Meeting, OSI2 Stockholders will not know or be able to calculate the market value of the Merger Consideration they would receive upon completion of the Mergers. Neither OSI2 nor OCSL is permitted to terminate the Merger Agreement or resolicit the vote of their respective stockholders solely because of changes in the market price of shares of OCSL Common Stock. There will be no adjustment to the Merger Consideration for changes in the market price of shares of OCSL Common Stock.

Changes in the market price of OCSL Common Stock may result from a variety of factors, including, among other things:

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These factors are generally beyond the control of OCSL. The range of high and low sales prices per share of OCSL Common Stock as reported on Nasdaq for the quarter ended September 30, 2022 was a low of $5.87 and a high of $7.25. However, historical trading prices are not necessarily indicative of future performance. OSI2 Stockholders should obtain current market quotations for shares of OCSL Common Stock prior to the OSI2 Special Meeting.

Sales of shares of OCSL Common Stock after the completion of the Mergers may cause the market price of OCSL Common Stock to decline.

At the Effective Time, each share of the OSI2 Common Stock, issued and outstanding immediately prior to the Effective Time (other than Cancelled Shares), will be converted into the right to receive a number of shares of OCSL Common Stock equal to the Exchange Ratio, plus any cash (without interest) in lieu of fractional shares. For illustrative purposes, based on September 30, 2022 NAVs and excluding transaction costs and other tax-related distributions, OCSL would issue approximately 2.72 shares of OCSL Common Stock for each share of OSI2 Common Stock outstanding, resulting in pro forma ownership of 79.5% for current OCSL Stockholders and 20.5% for current OSI2 Stockholders. Former OSI2 Stockholders may be required to or decide to sell the shares of OCSL Common Stock that they receive pursuant to the Merger Agreement, particularly because they have not previously held liquid securities. In addition, OCSL Stockholders may decide not to hold their shares of OCSL Common Stock after completion of the Mergers. In each case, such sales of OCSL Common Stock could have the effect of depressing the trading price for OCSL Common Stock and may take place promptly following the completion of the Mergers. If this occurs, it could impair OCSL’s ability to raise additional capital through the sale of equity securities should OCSL desire to do so.

OCSL Stockholders and OSI2 Stockholders will experience a reduction in percentage ownership and voting power in the combined company as a result of the Mergers.

OCSL Stockholders will experience a reduction in their percentage ownership interests and effective voting power in respect of the combined company relative to their percentage ownership interests in OCSL prior to the Mergers unless they hold a comparable or greater percentage ownership in OSI2 as they do in OCSL prior to the Mergers. Consequently, OCSL Stockholders should generally expect to exercise less influence over the management and policies of the combined company following the Mergers than they currently exercise over the management and policies of OCSL. OSI2 Stockholders will experience a substantial reduction in their percentage ownership interests and effective voting power in respect of the combined company relative to their percentage ownership interests in OSI2 prior to the Mergers unless they hold a comparable or greater percentage ownership in OCSL as they do in OSI2 prior to the Mergers. Consequently, OSI2 Stockholders should generally expect to

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exercise less influence over the management and policies of the combined company following the Mergers than they currently exercise over the management and policies of OSI2. In addition, prior to completion of the Mergers, subject to certain restrictions in the Merger Agreement, OCSL and OSI2 may issue additional shares of OCSL Common Stock and OSI2 Common Stock, respectively, which would further reduce the percentage ownership of the combined company to be held by current OCSL Stockholders and OSI2 Stockholders.

OCSL may be unable to realize the benefits anticipated by the Mergers, including estimated cost savings, or it may take longer than anticipated to achieve such benefits.

The realization of certain benefits anticipated as a result of the Mergers will depend in part on the integration of OSI2’s investment portfolio with OCSL’s investment portfolio and the integration of OSI2’s business with OCSL’s business. There can be no assurance that OSI2’s investment portfolio or business can be operated profitably going forward or integrated successfully into OCSL’s operations in a timely fashion or at all. The dedication of management resources to such integration may detract attention from the day-to-day business of the combined company and there can be no assurance that there will not be substantial costs associated with the transition process or there will not be other material adverse effects as a result of these integration efforts. Such effects, including incurring unexpected costs or delays in connection with such integration and failure of OSI2’s investment portfolio to perform as expected, could have a material adverse effect on the financial results of the combined company.

OCSL also expects to achieve certain synergies and cost savings from the Mergers when the two companies have fully integrated their portfolios. It is possible that the estimates of these synergies and potential cost savings could ultimately be incorrect. The cost savings estimates also assume OCSL will be able to combine its operations and OSI2’s operations in a manner that permits those cost savings to be fully realized. If the estimates turn out to be incorrect or if OCSL is not able to successfully combine OSI2’s investment portfolio or business with its operations, the anticipated synergies and cost savings may not be fully realized or realized at all or may take longer to realize than expected.

The opinion of the financial advisor to the OCSL Special Committee delivered to the OCSL Special Committee and the OCSL Board prior to the signing of the Merger Agreement and the opinion of the financial advisor to the OSI2 Special Committee delivered to the OSI2 Special Committee and the OSI2 Board prior to the signing of the Merger Agreement will not reflect changes in circumstances since the date of such opinions.

The opinion of Houlihan Lokey, the financial advisor to the OCSL Special Committee, was delivered to the OCSL Special Committee and the OCSL Board on, and was dated, September 14, 2022. The opinion of KBW, the financial advisor to the OSI2 Special Committee, was delivered to the OSI2 Special Committee and the OSI2 Board on, and was dated, September 14, 2022. Changes in OCSL’s or OSI2’s operations and prospects, general market and economic conditions and other factors that may be beyond the control of OCSL or OSI2 may significantly alter OSI2’s value or the price of shares of OCSL Common Stock by the time the Mergers are completed. The opinions do not speak as of the time the Mergers will be completed or as of any date other than the date of such opinions.

If the Mergers do not close for any reason (whether due to failure to obtain required stockholder approval or failure of either OCSL or OSI2 to satisfy certain closing conditions), OCSL and OSI2 will not benefit from the expenses incurred in pursuit of the Mergers.

The Mergers are subject to closing conditions, including certain approvals of OCSL Stockholders and OSI2 Stockholders that, if not satisfied, will prevent the Mergers from being completed. See “Description of the Merger Agreement Conditions to Closing the Mergers.” If the Mergers do not close, OCSL and OSI2 will have incurred substantial expenses for which no ultimate benefit will have been received. OCSL and OSI2 have incurred out-of-pocket expenses in connection with the Mergers for investment banking, legal and accounting fees and financial printing and other related charges, much of which will be incurred even if the Mergers are not completed.

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The termination of the Merger Agreement could negatively impact OCSL and OSI2.

If the Merger Agreement is terminated, there may be various consequences, including:

The Merger Agreement limits OCSL’s and OSI2’s ability to pursue alternatives to the Mergers.

The Merger Agreement contains provisions that limit OCSL’s and OSI2’s ability to discuss, facilitate or commit to competing third party proposals to acquire all or a significant part of OCSL or OSI2. These provisions, which are typical for transactions of this type, include a termination fee of $9.8 million payable by third parties to OCSL and $37.9 million payable by third parties to OSI2 under certain circumstances, might discourage a potential competing acquirer that might have an interest in acquiring all or a significant part of OCSL or OSI2 from considering or proposing that acquisition even if it were prepared to pay consideration with a higher per share market price than that proposed in the Mergers or might result in a potential competing acquirer proposing to pay a lower per share price to acquire OCSL or OSI2 than it might otherwise have proposed to pay.

The Mergers are subject to closing conditions, including stockholder approvals, that, if not satisfied or (to the extent legally allowed) waived, will result in the Mergers not being completed, which may result in material adverse consequences to the business and operations of OCSL and OSI2.

The Mergers are subject to closing conditions, including certain approvals of OCSL Stockholders and OSI2 Stockholders that, if not satisfied, will prevent the Mergers from being completed. The closing condition that OSI2 Stockholders adopt the Merger Agreement and approve the Merger Proposal may not be waived under applicable law and must be satisfied for the Mergers to be completed. If OSI2 Stockholders do not adopt the Merger Agreement and approve the Mergers and the Mergers are not completed, the resulting failure of the Mergers could have a material adverse impact on OCSL’s and OSI2’s respective businesses and operations. In addition, the closing condition that OCSL Stockholders approve the issuance of shares of OCSL Common Stock pursuant to the Merger Agreement may not be waived and must be satisfied for the Mergers to be completed. If OCSL Stockholders do not approve the Merger Stock Issuance Proposal and the Mergers are not completed, the resulting failure of the Mergers could have a material adverse impact on OCSL’s and OSI2’s respective businesses and operations. In addition to the required approvals of OCSL Stockholders and OSI2 Stockholders, the Mergers are subject to a number of other conditions beyond the control of OCSL and OSI2 that may prevent, delay or otherwise materially adversely affect completion of the Mergers. OCSL and OSI2 cannot predict whether and when these other conditions will be satisfied.

OCSL and OSI2 may, to the extent legally allowed, waive one or more conditions to the Mergers without resoliciting stockholder approval.

Certain conditions to OCSL’s and OSI2’s respective obligations to complete the Mergers may be waived, in whole or in part, to the extent legally allowed, either unilaterally or by mutual agreement. In the event that any such waiver does not require resolicitation of stockholders, OCSL and OSI2 will each have the discretion to complete the Mergers without seeking further stockholder approval. The conditions requiring the approval of OCSL Stockholders and OSI2 Stockholders, however, cannot be waived.

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OCSL and OSI2 will be subject to operational uncertainties and contractual restrictions while the Mergers are pending.

Uncertainty about the effect of the Mergers may have an adverse effect on OCSL or OSI2 and, consequently, on the combined company following completion of the Mergers. These uncertainties may cause those that deal with OCSL or OSI2 to seek to change their existing business relationships with them. In addition, the Merger Agreement restricts OCSL and OSI2 from taking actions that each might otherwise consider to be in its best interests. These restrictions may prevent OCSL or OSI2 from pursuing certain business opportunities that may arise prior to the completion of the Mergers.

The market price of OCSL Common Stock after the Mergers may be affected by factors different from those affecting such common stock currently.

OCSL’s business and OSI2’s business differ in some respects and, accordingly, the results of operations of the combined company and the market price of OCSL Common Stock after the Mergers may be affected by factors different from those currently affecting the independent results of operations of each of OCSL and OSI2, such as a larger stockholder base, a different portfolio composition and a different capital structure, and OCSL’s trading price. Accordingly, OCSL’s historical trading prices and financial results may not be indicative of these matters for the combined company following the Mergers.

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COMPARATIVE FEES AND EXPENSES

Comparative Fees and Expenses Relating to the Mergers

The following table is intended to assist OCSL Stockholders and OSI2 Stockholders in understanding the costs and expenses that an investor in shares of OCSL Common Stock or OSI2 Common Stock bears directly or indirectly and, based on the assumptions set forth below, the pro forma costs and expenses estimated to be incurred by the combined company in the first year following completion of the Mergers. OCSL and OSI2 caution you that the percentages of Other expenses indicated in the table below are an estimate and may vary. Except where the context suggests otherwise, whenever this document contains a reference to fees or expenses paid or to be paid by “you,” “OCSL” or “OSI2,” stockholders will indirectly bear such fees or expenses as investors in OCSL or OSI2, as applicable. The table below is based on information as of September 30, 2022 (except as noted below) and includes expenses of the applicable consolidated subsidiaries.

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For OSI2, the base management fee is calculated at an annual rate of 1.00% of the Gross Asset Value; provided that prior to a Qualified Listing the base management fee will not exceed 1.75% per annum of the Unleveraged Asset Value. From and after the date of a Qualified Listing, if any, the base management fee will increase to 1.50% per annum of OSI2’s Gross Asset Value. See Note 9 in the notes to the Consolidated Financial Statements in OSI2’s Quarterly Report on Form 10-Q (File No. 814-01281) for the quarter ended June 30, 2022 for additional information. This table assumes that OSI2’s Gross Asset Value is $578.2 million, which was the actual amount of OSI2’s total gross assets (excluding cash and cash equivalents) as of September 30, 2022.

Following completion of the Mergers, the combined company will be externally managed by Oaktree. The pro forma base management fee has been calculated in accordance with the OCSL Investment Advisory Agreement. The pro forma base management fee referenced in the table above is based on the combined gross assets (excluding cash and cash equivalents) of OCSL and OSI2 on a pro forma basis on September 30, 2022 and does not reflect the voluntary, irrevocable waiver by Oaktree of $9.0 million of base management fees payable to it as follows: $6.0 million at a rate of $1.5 million per quarter (with such amount appropriately prorated for any partial quarter) in the first year following closing of the Mergers and $3.0 million at a rate of $750,000 per quarter (with such amount appropriately prorated for any partial quarter) in the second year following closing of the Mergers. The pro forma base management fee net of the $1.5 million quarterly base management fee waiver in the year following closing of the Mergers would be 2.66% of net assets attributable to OCSL Common Stock.

With respect to OCSL, the second part of the incentive fee (the “capital gains incentive fee”) is determined and payable in arrears as of the end of each fiscal year (or upon termination of the OCSL Investment Advisory Agreement, as of the termination date). With respect to OSI2, the second part of the incentive fee (the “capital gains incentive fee”) is determined and payable in arrears as of the end of each calendar year (or upon termination of the OSI2 Investment Advisory Agreement, as of the termination date).

With respect to OCSL, commencing with the fiscal year ended September 30, 2019, the capital gains incentive fee equals 17.5% of OCSL’s realized capital gains, if any, on a cumulative basis from the beginning of the fiscal year ended September 30, 2019 through the end of each fiscal year, computed net of all realized capital losses and unrealized capital depreciation on a cumulative basis, less the aggregate amount of any previously paid capital gains incentive fees under the OCSL Investment Advisory Agreement. Any realized capital gains or losses and unrealized capital depreciation with respect to OCSL’s portfolio as of the end of the fiscal year ended September 30, 2018 are excluded from the calculation of the second part of the incentive fee. In addition, the calculation of realized capital gains, realized capital losses and unrealized capital depreciation does (1) not include any such amounts resulting solely from merger-related accounting adjustments in connection with the assets acquired in the OCSI Merger, including any premium or discount paid for the acquisition of such assets, solely to the extent that the inclusion of such merger-related accounting adjustments, in the aggregate, would result in an increase in the capital gains incentive fee and (2) include any such amounts associated with the investments acquired in such transaction

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for the period from October 1, 2018 to the date of closing of such transaction, solely to the extent that the exclusion of such amounts, in the aggregate, would result in an increase in the capital gains incentive fee. See note 10 in the notes to the Consolidated Financial Statements in OCSL’s Annual Report on Form 10-K (File No. 814-00755) for the fiscal year ended September 30, 2022 for additional information about the incentive fee payable by OCSL.

With respect to OSI2, the capital gains incentive fee equals 20% of OSI2’s realized capital gains, if any, on a cumulative basis from August 6, 2018, the date of OSI2’s initial closing, through the end of each calendar year, computed net of all realized capital losses on a cumulative basis and unrealized capital depreciation, less the aggregate amount of any previously paid capital gains incentive fee under the OSI2 Investment Advisory Agreement. See Note 9 in the notes to the Consolidated Financial Statements in OSI2’s Quarterly Report on Form 10-Q (File No. 814-01281) for the fiscal quarter ended June 30, 2022 for additional information for additional information about the incentive fee payable by OSI2.

For the “Actual” columns, the incentive fees referenced in the table above are based on actual amounts of the incentive fee on income incurred during the fiscal quarter ended September 30, 2022 and the capital gains incentive fee payable under the applicable investment advisory agreement as of September 30, 2022.

Following completion of the Mergers, the combined company will be externally managed by Oaktree. The pro forma incentive fees have been calculated in a manner consistent with the OCSL Investment Advisory Agreement.

OCSL will exclude any amounts resulting solely from the new cost basis of the acquired OSI2 investments established by ASC 805 as a result of the Mergers from the calculation of the incentive fee on income and the incentive fee on capital gains, with such exclusion to be implemented either through an amendment to the OCSL Investment Advisory Agreement or a waiver of such amounts by Oaktree.

For OCSL, this amount includes the annual expenses of Senior Loan Fund I LLC (“SLF JV I”) and the annual expenses of OCSI Glick JV LLC (the “Glick JV”). There are no fees paid by SLF JV I or the Glick JV to Oaktree. The annual expenses of SLF JV I and the Glick JV include interest payments on the subordinated notes held by OCSL’s joint venture partners, which represented 10.3% of such expenses for OCSL, and exclude interest payments on the subordinated notes held by OCSL. See note 3 in the notes to

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the Consolidated Financial Statements in OCSL’s Annual Report on Form 10-K (File No. 814-00755) for the fiscal year ended September 30, 2022 for more information on SLF JV I and the Glick JV.

The “Pro Forma” column assumes the sum of amounts for each of OCSL and OSI2 for the combined company following the Mergers.

Example

The following example demonstrates the projected dollar amount of total cumulative expenses that would be incurred over various periods with respect to a hypothetical investment in OCSL, OSI2 or the combined company’s common stock following completion of the Mergers on a pro forma basis, in each case assuming that OCSL, OSI2 and the combined company hold no cash or liabilities other than debt. In calculating the following expense amounts, each of OCSL and OSI2 has assumed that it would have no additional leverage and that its annual operating expenses would remain at the levels set forth in the tables above. Calculations for the pro forma combined company following the Mergers assume that the Mergers closed on September 30, 2022 and that the leverage and operating expenses of OCSL and OSI2 remain at the levels set forth in the tables above (and gives effect to the base management fee waivers described above). Transaction expenses related to the Mergers are not included in the following examples.

While the example assumes, as required by the SEC, a 5% annual return, performance of OCSL, OSI2 and the combined company will vary and may result in a return greater or less than 5%. The incentive fee based on pre-incentive fee net investment income under each of the OCSL Investment Advisory Agreement and the OSI2 Investment Advisory Agreement, which, assuming a 5% annual return, would either not be payable or would have an insignificant impact on the expense amounts shown above, is not included in the example. If sufficient returns are achieved on investments, including through the realization of capital gains, to trigger an incentive fee of a material amount, expenses, and returns to investors, would be higher. This example assumes that, as of October 1, 2022, the sum of realized capital losses and unrealized capital depreciation on a cumulative basis since October 1, 2020 for OCSL and since inception for OSI2 is zero. In addition, while the example assumes reinvestment of all distributions at NAV, participants in OCSL’s dividend reinvestment plan will receive a

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number of shares of OCSL Common Stock determined by dividing the total dollar amount of the cash distribution payable to a participant by either (i) the greater of (a) the current NAV per share of OCSL Common Stock and (b) 95% of the market price per share of OCSL Common Stock at the close of trading on the payment date fixed by the OCSL Board of Directors in the event that newly issued shares are used to satisfy the share requirements of the dividend reinvestment plan or (ii) the average purchase price, excluding any brokerage charges or other charges, of all shares of OCSL Common Stock purchased by the administrator of the dividend reinvestment plan in the event that shares are purchased in the open market to satisfy the share requirements of the dividend reinvestment plan, which may be at, above or below NAV.

The example and the expenses in the table above should not be considered a representation of OCSL’s, OSI2’s, or, following completion of the Mergers, the combined company’s, future expenses, and actual expenses may be greater or less than those shown.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This joint proxy statement/prospectus, including the documents incorporated by reference herein, contains statements that constitute forward-looking statements, which relate to OCSL, OSI2 or, following the Mergers, the combined company, regarding future events or the future performance or future financial condition of OCSL, OSI2 or, following the Mergers, the combined company. The forward-looking statements may include statements as to: future operating results of OCSL, OSI2 or, following the Mergers, the combined company and distribution projections; business prospects of OCSL, OSI2 or, following the Mergers, the combined company and the prospects of their portfolio companies; and the impact of the investments that OCSL, OSI2 or, following the Mergers, the combined company expect to make. Certain factors could cause actual results and conditions to differ materially from those projected, including the uncertainties associated with:

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In addition, words such as “anticipate,” “believe,” “expect,” “seek,” “plan,” “should,” “estimate,” “project” and “intend” indicate forward-looking statements, although not all forward-looking statements include these words. The forward-looking statements contained in this joint proxy statement/prospectus involve risks and uncertainties. The actual results could differ materially from those implied or expressed in the forward-looking statements for any reason, including the factors set forth in “Item 1A. Risk Factors” in Part I of each of OCSL’s Annual Report on Form 10-K (File No. 814-00755) for the fiscal year ended September  30, 2022 and OSI2’s Annual Report on Form 10-K (File No. 814-01281) for the fiscal year ended September 30, 2021 and in “Item 1A. Risk Factors” in Part II of each of OSI2’s Quarterly Reports on Form 10-Q (File No. 814-01281) for the quarters ended June 30, 2022 and March 31, 2022, as such factors may be updated from time to time in their periodic filings with the SEC, and elsewhere contained or incorporated by reference in this joint proxy statement/prospectus.

Other factors that could cause actual results to differ materially include:

OCSL and OSI2 have based the forward-looking statements included in this joint proxy statement/prospectus and documents incorporated by reference into this joint proxy statement/prospectus on information available to them on the applicable date of the relevant document, and they assume no obligation to update any such forward-looking statements. Although OCSL and OSI2 undertake no obligation to revise or update any forward-looking statements, whether as a result of new information, future events or otherwise, you are advised to consult any additional disclosures that they may make directly to you or through reports that OCSL and OSI2 in the future may file with the SEC, including annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K. This joint proxy statement/prospectus and documents incorporated by reference into this joint proxy statement/prospectus contain or may contain statistics and other data that have been obtained from or compiled from information made available by third-party service providers. Neither OCSL nor OSI2 has independently verified such statistics or data.

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CAPITALIZATION

The following table sets forth (1) OCSL’s and OSI2’s actual capitalization as of September 30, 2022 and (2) OCSL’s capitalization as adjusted to reflect the effects of the Mergers. You should read this table together with OCSL’s and OSI2’s consolidated financial statements incorporated by reference herein.

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THE OCSL ANNUAL MEETING

Date, Time and Place of the OCSL Annual Meeting

The OCSL Annual Meeting will be held virtually on January 20, 2023, at 10:00 a.m., Pacific Time (1:00 p.m. Eastern Time), at the following website: www.virtualshareholdermeeting.com/OCSL2023. This joint proxy statement/prospectus and the accompanying materials are being mailed on or about December 1, 2022 to stockholders of record of OCSL and are available at www.proxyvote.com.

Purpose of the OCSL Annual Meeting

At the OCSL Annual Meeting, OCSL Stockholders will be asked to approve each of (i) the nominees proposed by the OCSL Board in connection with the Director Proposal; (ii) the Auditor Proposal; (iii) the Merger Stock Issuance Proposal; and (iv) the Reverse Stock Split Proposal.

After careful consideration and, with respect to the Merger Stock Issuance Proposal, on the recommendation of the OCSL Special Committee, comprised solely of certain independent directors of OCSL, the OCSL Board unanimously recommends that OCSL Stockholders vote “FOR” the election of each of the nominees proposed by the OCSL Board in connection with the Director Proposal, “FOR” the Auditor Proposal, “FOR” the Merger Stock Issuance Proposal and “FOR” the Reverse Stock Split Proposal.

Record Date

The OCSL Record Date is November 28, 2022. The OCSL Record Date is established by the OCSL Board, and only holders of record of shares of OCSL Common Stock at the close of business on the OCSL Record Date are entitled to receive notice of the OCSL Annual Meeting and vote at the OCSL Annual Meeting. As of the OCSL Record Date, there were 183,374,250 shares of OCSL Common Stock outstanding. Each share of OCSL Common Stock held by a holder of record as of the OCSL Record Date has one vote on each matter considered at the OCSL Annual Meeting.

Quorum and Adjournments

For OCSL to conduct business at the OCSL Annual Meeting, a quorum of OCSL Stockholders must be present. The presence at the OCSL Annual Meeting, virtually or by proxy, of the holders of a majority of the shares of OCSL Common Stock outstanding on the OCSL Record Date will constitute a quorum. Votes to “withhold authority” and abstentions will be treated as shares present for quorum purposes. Shares for which brokers have not received voting instructions from the beneficial owner of the shares and do not have discretionary authority to vote on certain proposals (which are considered “broker non-votes” with respect to such proposals) will be treated as shares present for quorum purposes at the OCSL Annual Meeting.

Pursuant to OCSL’s bylaws, the chairman of the OCSL Annual Meeting shall have the power to adjourn the OCSL Annual Meeting, whether or not a quorum is present, from time to time for any reason and without notice other than announcement at the OCSL Annual Meeting.

Broker Non-Votes

Broker non-votes are described as votes cast by a broker or other nominee on behalf of a beneficial holder who does not provide explicit voting instructions to such broker or nominee and who does not attend the meeting.

The Director Proposal is expected to be a non-routine matter for OCSL. As a result, if an OCSL Stockholder holds shares in “street name” through a broker, bank or other nominee, the broker, bank or nominee will not be

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permitted to exercise voting discretion with respect to the Director Proposal. Votes to “withhold authority” and broker non-votes, if any, will not be included in determining the number of votes cast and, as a result, will have no effect on the voting outcome of the Director Proposal.

The Auditor Proposal is expected to be a routine matter for OCSL. As a result, if an OCSL Stockholder holds shares in “street name” through a broker, bank or other nominee, the broker, bank or nominee will be permitted to exercise voting discretion with respect to the Auditor Proposal. Abstentions and broker non-votes, if any, will not be included in determining the number of votes cast and, as a result, will have no effect on the voting outcome of the Auditor Proposal.

The Merger Stock Issuance Proposal is expected to be a non-routine matter for OCSL. As a result, if an OCSL Stockholder holds shares in “street name” through a broker, bank or other nominee, the broker, bank or nominee will not be permitted to exercise voting discretion with respect to the Merger Stock Issuance Proposal. Abstentions and broker non-votes, if any, will not be included in determining the number of votes cast and, as a result, will have no effect on the voting outcome of the Merger Stock Issuance Proposal.

The Reverse Stock Split Proposal is expected to be a routine matter for OCSL. As a result, if an OCSL Stockholder holds shares in “street name” through a broker, bank or other nominee, the broker, bank or nominee will be permitted to exercise voting discretion with respect to the Reverse Stock Split Proposal. Abstentions and broker non-votes, if any, will have the effect of a vote “against” the Reverse Stock Split Proposal.

Vote Required

The affirmative vote of a plurality of the shares of OCSL Common Stock outstanding and entitled to vote thereon at the OCSL Annual Meeting is required to elect each director nominee of OCSL (i.e., the candidate receiving the most “for” votes will win each election). Stockholders may not cumulate their votes.

The affirmative vote of the holders of a majority of the votes cast by the holders of outstanding shares of OCSL Common Stock at the OCSL Annual Meeting in person or by proxy at a meeting at which a quorum is present is required for approval of the Auditor Proposal and the Merger Stock Issuance Proposal (i.e., the number of shares voted “for” the proposal must exceed the number of shares voted “against” such proposal).

The affirmative vote of a majority of the outstanding shares of OCSL Common Stock is required for approval of the Reverse Stock Split Proposal.

Voting of Management and Oaktree

On the OCSL Record Date, OCSL’s executive officers and directors owned and were entitled to vote approximately 653,336 shares of OCSL Common Stock, representing approximately 0.4% of the outstanding shares of OCSL Common Stock on the OCSL Record Date. None of OCSL’s executive officers or directors has entered into any voting agreement relating to the Mergers. OCM and certain affiliates, including Atlas OCM Holdings, LLC, intend to vote their shares of OCSL Common Stock “FOR” the approval of the Merger Stock Issuance Proposal. Pursuant to the voting agreement described under “Control Persons and Principal Stockholders of OCSL”, OCM also intends to direct Leonard Tannenbaum to vote the shares of OCSL Common Stock subject to such voting agreement “FOR” the approval of the Merger Stock Issuance Proposal.

Voting of Proxies

OCSL encourages OCSL Stockholders to vote their shares, either by voting at the OCSL Annual Meeting or by voting by proxy, which means that OCSL Stockholders authorize someone else to vote their shares. Shares represented by duly executed proxies will be voted in accordance with OCSL Stockholders’ instructions. If OCSL Stockholders execute a proxy without specifying their voting instructions, such OCSL Stockholders’

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shares will be voted in accordance with the OCSL Board’s recommendation. If any other business is brought before the OCSL Annual Meeting, OCSL Stockholders’ shares will be voted at the OCSL Board’s discretion unless OCSL Stockholders specifically state otherwise on their proxy.

An OCSL Stockholder may also authorize a proxy by telephone or through the Internet using the toll-free telephone numbers or web address printed on your proxy card. Authorizing a proxy by telephone or through the Internet requires you to input the control number located on your proxy card. After inputting the control number, you will be prompted to direct your proxy to vote on each proposal. You will have an opportunity to review your directions and make any necessary changes before submitting your directions and terminating the telephone call or Internet link.

Important notice regarding the availability of proxy materials for the OCSL Annual Meeting. OCSL’s joint proxy statement/prospectus, OCSL’s Annual Report on Form 10-K for the year ended September 30, 2022 and the proxy card are available at www.proxyvote.com.

Revocability of Proxies

If you are a stockholder of record of OCSL, you can revoke your proxy as to OCSL at any time before it is exercised by: (i) delivering a written revocation notice that is received prior to the OCSL Annual Meeting to Oaktree Specialty Lending Corporation, 333 South Grand Avenue, 28th Floor, Los Angeles, CA 90071, Attention: Secretary; (ii) submitting a later-dated proxy that OCSL receives before the conclusion of voting at the OCSL Annual Meeting; or (iii) participating in the OCSL Annual Meeting and voting online. If you hold shares of OCSL Common Stock through a broker, bank, trustee or nominee, you must follow the instructions you receive from them in order to revoke your voting instructions. Participating in the OCSL Annual Meeting does not revoke your proxy unless you also vote online at the OCSL Annual Meeting.

Solicitation of Proxies

OCSL and OSI2 will bear the cost of preparing, printing and mailing this joint proxy statement/prospectus and the accompanying Notice of Annual Meeting of Stockholders of OCSL or Notice of Special Meeting of Stockholders of OSI2, as applicable, and proxy cards based on their respective numbers of stockholders. OCSL and OSI2 intend to use the services of Broadridge to aid in the distribution and collection of proxies for an estimated fee of approximately $58,000 plus pass through charges. No additional compensation will be paid to directors, officers or Oaktree employees for such services. For more information regarding expenses related to the Mergers, see “Questions and Answers about the Mergers — Who is responsible for paying the expenses relating to completing the Mergers?”

Appraisal Rights

OCSL Stockholders do not have the right to exercise appraisal rights with respect to any matter to be voted upon at the OCSL Annual Meeting. To the extent that an OCSL Stockholder objects to the Merger Stock Issuance Proposal, such OCSL Stockholder will not have the right to have a court judicially determine (and the OCSL Stockholder will not receive) the fair value for its shares of OCSL Common Stock under the provisions of Delaware law governing appraisal rights.

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THE OSI2 SPECIAL MEETING

Date, Time and Place of the OSI2 Special Meeting

The OSI2 Special Meeting will be held virtually on January 20, 2023, at 10:30 a.m., Pacific Time (1:30 p.m. Eastern Time), at the following website: www.virtualshareholdermeeting.com/OSI22023SM. This joint proxy statement/prospectus and the accompanying materials are being mailed on or about December 1, 2022 to stockholders of record of OSI2 and are available at www.proxyvote.com.

Purpose of the OSI2 Special Meeting

At the OSI2 Special Meeting, OSI2 Stockholders will be asked to approve the Merger Proposal.

After careful consideration, on the recommendation of the OSI2 Special Committee, comprised solely of certain independent directors of OSI2, the OSI2 Board unanimously approved the Merger Agreement and the transactions contemplated thereby, including the Mergers, and unanimously recommends that OSI2 Stockholders vote “FOR” the Merger Proposal.

Record Date

The OSI2 Record Date is November 28, 2022. The OSI2 Record Date is established by the OSI2 Board, and only holders of record of shares of OSI2 Common Stock at the close of business on the OSI2 Record Date are entitled to receive notice of the OSI2 Special Meeting and vote at the OSI2 Special Meeting. As of the OSI2 Record Date, there were 17,401,121 shares of OSI2 Common Stock outstanding. Each share of OSI2 Common Stock held by a holder of record as of the OSI2 Record Date has one vote on each matter considered at the OSI2 Special Meeting.

Quorum and Adjournments

For OSI2 to conduct business at the OSI2 Special Meeting, a quorum of OSI2 Stockholders must be present. The presence at the OSI2 Special Meeting, virtually or by proxy, of the holders of a majority of the shares of OSI2 Common Stock outstanding on the OSI2 Record Date will constitute a quorum of OSI2. Abstentions will be treated as shares present for quorum purposes. Broker non-votes, if any, will not be treated as shares present for quorum purposes at the OSI2 Special Meeting.

Pursuant to OSI2’s bylaws, if less than a quorum is present at the OSI2 Special Meeting or if an insufficient number of votes is present for the adoption of the Merger Proposal at such meeting, the chairman of the OSI2 Special Meeting or OSI2 stockholders holding a majority of the shares of OSI2 Common Stock will have the power to adjourn the OSI2 Special Meeting from time to time without notice other than announcement at the OSI2 Special Meeting until a quorum is present.

Broker Non-Votes

Broker non-votes are described as votes cast by a broker or other nominee on behalf of a beneficial holder who does not provide explicit voting instructions to such broker or nominee and who does not attend the meeting. The Merger Proposal is a non-routine matter for OSI2. As a result, if an OSI2 Stockholder holds shares in “street name” through a broker, bank, or other nominee, the broker, bank or nominee will not be permitted to exercise voting discretion with respect to the Merger Proposal. Because the sole proposal at the OSI2 Special Meeting is the Merger Proposal, OSI2 does not expect any broker non-votes. However, if shares representing broker non-votes are presented at the OSI2 Special Meeting, such shares will not count as affirmative votes cast and will therefore have the same effect as votes “against” the Merger Proposal.

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Vote Required

The affirmative vote of the holders of a majority of the outstanding shares of OSI2 Common Stock is required to approve the OSI2 Merger Proposal. Abstentions and broker non-votes, if any, will have the effect of a vote “against” this proposal. Proxies received will be voted “FOR” the Merger Proposal, unless OSI2 Stockholders designate otherwise.

Voting of Management

On the OSI2 Record Date, OSI2’s executive officers and directors did not own any shares of OSI2 Common Stock. None of OSI2’s executive officers or directors has entered into any voting agreement relating to the Mergers.

Voting of Proxies

OSI2 encourages OSI2 Stockholders to vote their shares, either by voting at the OSI2 Special Meeting or by voting by proxy, which means that OSI2 Stockholders authorize someone else to vote their shares. Shares represented by duly executed proxies will be voted in accordance with OSI2 Stockholders’ instructions. If OSI2 Stockholders execute a proxy without specifying their voting instructions, such OSI2 Stockholders’ shares will be voted in accordance with the OSI2 Board’s recommendation. If any other business is brought before the OSI2 Special Meeting, the OSI2 Stockholders’ shares will be voted at the OSI2 Board’s discretion unless the OSI2 Stockholders specifically state otherwise on their proxy.

An OSI2 Stockholder may also authorize a proxy by telephone or through the Internet using the toll-free telephone numbers or web address printed on your proxy card. Authorizing a proxy by telephone or through the Internet requires you to input the control number located on your proxy card. After inputting the control number, you will be prompted to direct your proxy to vote on each proposal. You will have an opportunity to review your directions and make any necessary changes before submitting your directions and terminating the telephone call or Internet link.

Important notice regarding the availability of proxy materials for the OSI2 Special Meeting. OSI2’s joint proxy statement/prospectus and the proxy card are available at www.proxyvote.com.

Revocability of Proxies

If you are a stockholder of record of OSI2, you can revoke your proxy as to OSI2 at any time before it is exercised by: (i) delivering a written revocation notice that is received prior to the OSI2 Special Meeting to Oaktree Strategic Income II, Inc., 333 South Grand Avenue, 28th Floor, Los Angeles, CA 90071, Attention: Secretary; (ii) submitting a later-dated proxy that OSI2 receives before the conclusion of voting at the OSI2 Special Meeting; or (iii) participating in the OSI2 Special Meeting and voting online. If you hold shares of OSI2 Common Stock through a broker, bank, trustee or nominee, you must follow the instructions you receive from them in order to revoke your voting instructions. Participating in the OSI2 Special Meeting does not revoke your proxy unless you also vote online at the OSI2 Special Meeting.

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Solicitation of Proxies

OCSL and OSI2 will bear the cost of preparing, printing and mailing this joint proxy statement/prospectus and the accompanying Notice of Annual Meeting of Stockholders of OCSL or Notice of Special Meeting of Stockholders of OSI2, as applicable, and proxy cards based on their respective numbers of stockholders. OCSL and OSI2 intend to use the services of Broadridge to aid in the distribution and collection of proxies for an estimated fee of approximately $58,000 plus pass through charges. No additional compensation will be paid to directors, officers or Oaktree employees for such services. For more information regarding expenses related to the Mergers, see “Questions and Answers about the Mergers — Who is responsible for paying the expenses relating to completing the Mergers?”

Appraisal Rights

OSI2 Stockholders do not have the right to exercise appraisal rights with respect to any matter to be voted upon at the OSI2 Special Meeting. To the extent that an OSI2 Stockholder objects to the Mergers, such OSI2 Stockholder will not have the right to have a court judicially determine (and the OSI2 Stockholder will not receive) the fair value for its shares of OSI2 Common Stock under the provisions of Delaware law governing appraisal rights.

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THE MERGERS

The discussion in this joint proxy statement/prospectus, which includes the material terms of the Mergers and the principal terms of the Merger Agreement, is subject to, and is qualified in its entirety by reference to, the Merger Agreement, a copy of which is attached as Annex A to this joint proxy statement/prospectus.

General Description of the Mergers

Pursuant to the terms of the Merger Agreement, at the Effective Time, Merger Sub will be merged with and into OSI2. OSI2 will be the surviving company and will continue its existence as a corporation under the laws of the State of Delaware and a direct, wholly-owned subsidiary of OCSL. As of the Effective Time, the separate corporate existence of Merger Sub will cease. Immediately after the effectiveness of the Merger, OSI2 will merge with and into OCSL, with OCSL as the surviving entity in the Second Merger. As of the Second Effective Time, the separate corporate existence of OSI2 will cease. Subject to the terms and conditions of the Merger Agreement, at the Effective Time, each share of OSI2 Common Stock issued and outstanding immediately prior to the Effective Time (other than Cancelled Shares) will be converted into the right to receive a number of shares of OCSL Common Stock equal to the Exchange Ratio, plus any cash in lieu of fractional shares.

Based on the number of shares of OCSL Common Stock issued and outstanding and the NAVs of OCSL and OSI2 as of September 30, 2022 (and excluding transaction costs and tax-related distributions), OCSL would issue approximately 2.72 shares of OCSL Common Stock for each share of OSI2 Common Stock outstanding, resulting in pro forma ownership of 79.5% for current OCSL Stockholders and 20.5% for current OSI2 Stockholders.

Background of the Mergers

Since an affiliate of Oaktree became investment adviser to OCSL in October 2017, the OCSL Board has met regularly to provide governance and oversight for the ongoing operation of OCSL’s business, with a focus on generating current income and capital appreciation. Among other items, at these meetings, the OCSL Board periodically reviewed long-term strategic plans for OCSL, as well as potential business opportunities. As part of these ongoing discussions, Oaktree and its affiliates have explored means of improving the trading price of OCSL Common Stock and enhancing the size and scale of OCSL. Oaktree and the OCSL Board have focused their efforts on opportunities to provide additional scale to OCSL because of the general tendency of Business Development Companies with smaller market capitalizations to trade at a larger discount or smaller premium to NAV than larger Business Development Companies. In addition, Oaktree and its affiliates have discussed with the OCSL Board means of attracting additional equity research analyst coverage and institutional investors, as additional interest in the stock by potential investors could yield additional secondary market activity (thereby improving liquidity), improve the trading price of OCSL Common Stock and otherwise make raising equity capital in the future easier.

As part of these reviews of long-term strategic plans for OCSL, Oaktree and its affiliates regularly review with the OCSL Board potential mergers, acquisitions, joint ventures and other similar transaction opportunities that could enhance OCSL Stockholder value, including opportunities related to OCSL’s existing joint ventures. From time to time, Oaktree and its affiliates have presented to the OCSL Board, and the OCSL Board has considered and discussed, possible strategic transactions that were available to OCSL and the potential benefits and risks of such transactions.

As a result of these reviews and discussions, on October 28, 2020, OCSL entered into an Agreement and Plan of Merger (the “OCSI Merger Agreement”) with OCSI, Lion Merger Sub, Inc., OCSL’s wholly-owned subsidiary, and, solely for the limited purposes set forth therein, Oaktree. On March 19, 2021, pursuant to the OCSI Merger Agreement, OCSL acquired OCSI in the OCSI Merger. Since the OCSI Merger, Oaktree has continued to explore opportunities to enhance OCSL Stockholder value and further increase the scale of OCSL.

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Oaktree and its affiliates regularly reviewed with the OCSL Board the impacts of the OCSI Merger on OCSL, including realization of expense savings, increased liquidity and increased access to debt capital.

In connection with the initial private offering of OSI2 Common Stock, OSI2 disclosed to investors that if OSI2 had not completed a “Liquidity Event” (as defined below) by the fifth anniversary of its initial closing, or August 6, 2023, the OSI2 Board (subject to any necessary stockholder approvals and applicable requirements of the Investment Company Act) will use its best efforts to wind down and/or liquidate and dissolve OSI2, subject to its right to engage in certain runoff activities. A “Liquidity Event” was defined as, at the discretion of the OSI2 Board: (a) a Qualified Listing (as defined below) or (b) with the consent of a majority of outstanding shares of OSI2 Common Stock not affiliated with Oaktree and in accordance with the applicable requirements of Delaware law, a corporate control transaction, which may include a strategic sale of OSI2 or all or substantially all of OSI2’s assets to, or a merger with, another entity, or another type of corporate control event, which may include, but is not limited to, a transaction with an affiliated entity, including an affiliated Business Development Company, for consideration in cash or publicly listed securities of such entity or a combination of cash and such publicly listed securities. For purposes of the above, a “Qualified Listing” is: (i) the listing of OSI2 Common Stock on a national securities exchange or (ii) an initial public offering of OSI2 Common Stock that results in gross proceeds to OSI2 of at least $50 million and a listing of OSI2 Common Stock on a national securities exchange. OSI2 refers collectively to a Liquidity Event and the wind down and/or liquidation and dissolution of OSI2, subject to its right to engage in certain runoff activities, as the “Liquidity Alternatives.”

On July 29, 2022, at a regular telephonic and video meeting of the OCSL Board, with representatives of Oaktree, Stradley Ronon Stevens & Young, LLP (“Stradley”), counsel to the OCSL Independent Directors, and Kirkland & Ellis LLP (“Kirkland”), counsel to Oaktree and OCSL, also in attendance, representatives of Oaktree proposed the Mergers. Before discussion of the proposed Mergers began and after discussion among the members of the OCSL Board, the OCSL Board determined to form a special committee (the “OCSL Special Committee”) to analyze and evaluate the Mergers and, as appropriate, to negotiate the terms of the Mergers on behalf of OCSL, with the OCSL Special Committee to consist of the OCSL Independent Directors other than Ms. Gero.

The OCSL Board then established the OCSL Special Committee and authorized it to, among other things: (1) review, evaluate, consider and, as appropriate, negotiate the terms and conditions of the Mergers and any agreements or arrangements proposed to be entered into by OCSL in connection with or relating to the Mergers, including to determine whether the Mergers are advisable and in the best interests of all OCSL Stockholders and whether the interests of OCSL Stockholders will be diluted as a result of the Mergers; (2) recommend to the full OCSL Board what action, if any, should be taken by the OCSL Board with respect to the Mergers and any such agreements or arrangements proposed to be entered into in connection with or relating to the Mergers; (3) hire any advisors that they deemed appropriate, including their own legal counsel and financial advisor; and (4) take such other actions as the OCSL Special Committee may deem to be necessary or appropriate for the OCSL Special Committee to discharge its duties. The OCSL Board determined to proceed with the Mergers only if the OCSL Special Committee (a) determined that the Mergers are advisable and in the best interests of all OCSL Stockholders and that the interests of OCSL Stockholders will not be diluted for purposes of Rule 17a-8 of the Investment Company Act as a result of the Mergers and (b) recommended to the full OCSL Board to approve the Mergers. The OCSL Special Committee was not obligated to recommend the Mergers or any agreements or arrangements proposed to be entered into by OCSL in connection with or relating to the Mergers to the OCSL Board and was authorized to determine, if the OCSL Special Committee deemed appropriate, that it was in the best interests of OCSL and OCSL Stockholders not to proceed with the Mergers.

The OCSL Board then temporarily adjourned its regular telephonic and video meeting and the OCSL Special Committee convened a special telephonic and video meeting. Representatives of Oaktree, Stradley and Kirkland also attended at the request of the OCSL Special Committee. The OCSL Special Committee engaged Stradley to represent the OCSL Special Committee in its evaluation and negotiation of the Mergers. It was also noted that Oaktree and OCSL had provided waivers to enable Kirkland to provide joint representation to each of

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OCSL (but not the OCSL Special Committee) and Oaktree in the proposed transaction, which was consistent with industry practice in other affiliated investment company mergers. Representatives of Oaktree then outlined an initial proposal for the Mergers, including that the proposed consideration to be paid to OSI2 Stockholders would be determined based on the relative NAVs of OCSL and OSI2 within 48 hours (excluding Sundays and holidays) prior to consummation of the Mergers (a so-called “NAV-for-NAV” transaction). Oaktree noted that the transaction structure for the Mergers would be similar to that of the OCSI Merger. Oaktree provided the OCSL Special Committee with additional background regarding OSI2, noting the extensive overlap between the OCSL and OSI2 portfolios. Oaktree then discussed the potential benefits of the Mergers to OCSL, including the potential for increased scale and secondary market liquidity, the possibility of broader research analyst coverage, acquiring a known portfolio of assets, enhanced access to debt capital markets at potentially more attractive pricing, accretion of net investment income per share and potential expense savings, as well as the potential negative considerations in connection with the Mergers, including any inability to receive the necessary stockholder approvals, potential pressures on the price of OCSL Common Stock if OSI2 Stockholders sell the shares received in the Mergers, the time and ability needed to ramp up to target leverage ratios, the potential for frivolous litigation and transaction costs. Oaktree representatives also reviewed key assumptions and discussed the financial model for the Mergers, which reflected a waiver of a portion of OCSL’s management fees for a period of two years following closing of the Mergers, and the anticipated capital structure for the combined company post-Mergers. The OCSL Special Committee then discussed the proposed Mergers and asked questions of Oaktree, Kirkland and Stradley. After discussion, the OCSL Special Committee decided to continue exploring the proposed Mergers and asked representatives of Oaktree to schedule a meeting of the OCSL Special Committee to discuss the engagement by the OCSL Special Committee of a financial advisor to advise it in connection with the transaction. The OCSL Special Committee also directed Kirkland to begin preparation of the draft Merger Agreement for review by the OCSL Special Committee and Stradley.

On August 5, 2022, at a regular telephonic and video meeting of the OSI2 Board, with representatives of Oaktree and Sullivan & Cromwell LLP (“Sullivan & Cromwell”), counsel to OSI2, also in attendance, representatives of Oaktree proposed potential Liquidity Alternatives for the OSI2 Board’s consideration, and representatives of Oaktree reminded the OSI2 Board that (i) OSI2’s investment period is scheduled to expire on August 6, 2023, (ii) different Liquidity Alternatives have different lead times and (iii) OSI2 Stockholders were informed at the time of their investment that if OSI2 did not complete a “Liquidity Event” on or prior to the fifth anniversary of the date of OSI2’s initial closing of its offering of shares of OSI2 Common Stock, August 6, 2023, the OSI2 Board would be obligated to use its best efforts to wind down and/or liquidate and dissolve OSI2 (subject to its right to engage in certain runoff activities). Before discussion of the proposed Mergers began and after discussion and upon the advice of Sullivan & Cromwell, the OSI2 Board determined to form a special committee (the “OSI2 Special Committee”), with the OSI2 Special Committee to analyze and evaluate any Liquidity Alternatives and, as appropriate, to negotiate the terms of such Liquidity Alternatives on behalf of OSI2, to consist of the OSI2 Independent Directors other than Ms. Gero.

The OSI2 Board then established the OSI2 Special Committee and authorized it to, among other things: (i) review, evaluate, consider and negotiate the terms and conditions of any Liquidity Alternatives and any agreements or arrangements proposed to be entered into by OSI2 in connection with or relating to any Liquidity Alternatives, including to determine whether the interests of OSI2 Stockholders would be diluted for purposes of Rule 17a-8 of the Investment Company Act; (ii) recommend to the OSI2 Board what action, if any, should be taken by the OSI2 Board with respect to any Liquidity Alternative and any such agreements or arrangements proposed to be entered into in connection with or relating to any Liquidity Alternatives; (iii) hire any advisors that the OSI2 Special Committee deems appropriate; (iv) take any such other actions as the OSI2 Special Committee may deem to be necessary or appropriate for the OSI2 Special Committee to discharge its duties; (v) provide reports or recommendations to the OSI2 Board in regard to such matters at such times as the OSI2 Special Committee deemed appropriate and consistent with its activities; and (vi) recommend, or not to recommend, to the OSI2 Board any Liquidity Alternative, and to determine whether or not it is in the best interests of OSI2 and the OSI2 Stockholders that OSI2 proceed with any Liquidity Alternative. Ms. Gero then temporarily dropped from the meeting for the remainder of the discussion regarding Liquidity Alternatives. As

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part of this discussion, representatives of Oaktree presented to the OSI2 Board on various Liquidity Alternatives, including the proposed Mergers.

At the end of this discussion, the OSI2 Special Committee discussed with representatives of Oaktree and Sullivan & Cromwell its options with respect to engaging a financial advisor to assist with its evaluation of the Liquidity Alternatives, and the OSI2 Special Committee determined to proceed with engaging a financial advisor. The OSI2 Special Committee selected certain nationally recognized investment banks to interview for the role of financial advisor to the OSI2 Special Committee in connection with its evaluation of the Liquidity Alternatives and directed Oaktree management to coordinate scheduling interviews.

On August 9, 2022, the OCSL Special Committee held a special telephonic and video meeting. Representatives of Oaktree, Stradley and Kirkland also attended at the request of the OCSL Special Committee. The OCSL Special Committee discussed its options with respect to engaging a financial advisor for the proposed Mergers. After discussion, the OCSL Special Committee decided to proceed with engaging a financial advisor to provide financial advisory services and evaluate the potential Mergers and selected certain nationally recognized investment banks to interview for the role of financial advisor to the OCSL Special Committee in connection with the Mergers and directed Oaktree management to coordinate scheduling interviews. The OCSL Special Committee then discussed the benefits and costs of seeking a fairness opinion from a financial advisor, noting the input of each of the investment banks to be interviewed for the role of financial advisor would be sought. Representatives of Oaktree then outlined a proposed timeline for the transaction and responded to questions from the OCSL Special Committee. At the request of the OCSL Special Committee, representatives of Kirkland and Stradley discussed with the OCSL Special Committee the fiduciary duties of the directors under Delaware law and considerations under the Investment Company Act, which were further documented in a written memorandum from Kirkland, and responded to questions from the OCSL Special Committee.

On August 13, 2022 and August 15, 2022, Kirkland and Sullivan & Cromwell exchanged correspondence regarding certain structural considerations in connection with the proposed Mergers, which was intended to assist the OCSL Special Committee in its consideration of the Mergers and to assist the OSI2 Special Committee in its consideration of the proposed Mergers as a Liquidity Alternative.

On August 15, 2022, Kirkland circulated a draft of the Merger Agreement to Stradley and the OCSL Special Committee.

On August 16, 2022, Kirkland exchanged correspondence with the OCSL Special Committee and Stradley regarding the draft Merger Agreement, responding to questions and comments from the OCSL Special Committee.

Later on August 16, 2022, the OCSL Special Committee held a special telephonic and video meeting to interview certain nationally recognized investment banks as financial advisor candidates in connection with its consideration of the Mergers and solicit their views regarding the benefits and costs of seeking a fairness opinion. Representatives of Stradley and Kirkland also attended at the request of the OCSL Special Committee. The OCSL Special Committee evaluated, among other things, the strengths and weaknesses of the presentations made by the financial advisor candidates and each investment bank’s experience with transactions involving Business Development Companies, their ability to provide high-quality financial advice and assistance with respect to the proposed transaction and estimated fees to be charged in connection with a potential engagement. After evaluating the qualifications of the investment banks, including whether such candidates had relationships with OSI2, OCSL or Oaktree and its affiliates, the OCSL Special Committee authorized the engagement of Houlihan Lokey as the financial advisor to the OCSL Special Committee and directed Kirkland and Stradley to proceed with negotiation of the Houlihan Lokey engagement letter, in consultation with the OCSL Special Committee. Representatives of Kirkland and Stradley then discussed the draft Merger Agreement with the OCSL Special Committee, highlighting certain differences from the OCSI Merger Agreement and the reasons for such differences, following which the OCSL Special Committee authorized continued negotiation of the transaction.

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Subsequent to the meeting, Houlihan Lokey was engaged to act as the financial advisor to the OCSL Special Committee.

On August 18, 2022, Stradley provided comments on the draft Merger Agreement and directed Kirkland to provide the revised draft to Sullivan & Cromwell.

Also on August 18, 2022, the OSI2 Special Committee interviewed certain nationally recognized investment banks as financial advisor candidates in connection with its consideration of the Liquidity Alternatives. Representatives of Sullivan & Cromwell were in attendance for these interviews. Immediately following the aforementioned interviews, the OSI2 Special Committee held a special telephonic and video meeting with representatives of Sullivan & Cromwell and Oaktree in attendance at the request of the OSI2 Special Committee. Representatives of Oaktree then discussed the potential timeline for the proposed Mergers, in the event the OSI2 Special Committee determined to pursue the Mergers as a Liquidity Alternative. Representatives of Sullivan & Cromwell discussed with the OSI2 Special Committee the fiduciary duties of the directors under Delaware law and considerations under the Investment Company Act, which were further documented in a written presentation from Sullivan & Cromwell, and responded to questions from the OSI2 Special Committee. The OSI2 Special Committee then evaluated, among other things, the strengths and weaknesses of the financial advisor candidates based on their interviews and each investment bank’s qualifications, experience with transactions involving Business Development Companies, their ability to provide high-quality financial advice and assistance with respect to the proposed Liquidity Alternatives and estimated fees proposed for their services in connection with a potential engagement. After evaluating the qualifications of the investment banks, including whether such candidates had relationships with OSI2, OCSL or Oaktree and its affiliates, the OSI2 Special Committee authorized the engagement of KBW as the financial advisor to the OSI2 Special Committee. Subsequent to the meeting, KBW was engaged to act as the financial advisor to the OSI2 Special Committee.

On August 19, 2022, Kirkland circulated a draft of the Merger Agreement to Sullivan & Cromwell, which draft reflected feedback from Stradley and the OCSL Special Committee.

On August 20, 2022, Kirkland circulated a revised draft of the Merger Agreement to the OCSL Special Committee and Stradley.

On August 25, 2022, representatives of Sullivan & Cromwell and Kirkland had a telephone conference to discuss the draft Merger Agreement and certain provisions contained therein.

Also on August 25, 2022, Sullivan & Cromwell circulated comments to the draft Merger Agreement to the OSI2 Special Committee.

On August 26, 2022, the OSI2 Special Committee held a special telephonic and video meeting with representatives of Sullivan & Cromwell also in attendance, at the request of the OSI2 Special Committee, to discuss the key terms of Kirkland’s draft of the Merger Agreement, including, among other terms, deal protections, conditions to closing, and termination rights, and comments to the draft Merger Agreement, to provide the OSI2 Special Committee with further information on the proposed Mergers for purposes of the OSI2 Special Committee’s consideration of the Liquidity Alternatives. Representatives of Sullivan & Cromwell responded to questions from the OSI2 Special Committee. Representatives of Sullivan & Cromwell then provided an update on the proposed timeline for the proposed Mergers, following which the OSI2 Special Committee authorized negotiation of the transaction in the event that the OSI2 Special Committee chose to pursue the proposed Mergers as a Liquidity Alternative. Subsequent to the meeting, Sullivan & Cromwell provided comments on the draft Merger Agreement, which reflected feedback from the OSI2 Special Committee, to Kirkland.

On August 27, 2022, Kirkland circulated the comments received from Sullivan & Cromwell on the Merger Agreement to the OCSL Special Committee and Stradley, along with an outline of proposed responses, to which the OCSL Special Committee expressed their agreement.

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On August 29, 2022, the OCSL Special Committee held a special telephonic and video meeting. Representatives of Oaktree, EY, Houlihan Lokey, Stradley and Kirkland also attended at the request of the OCSL Special Committee. Houlihan Lokey provided the OCSL Special Committee with its preliminary analysis of OSI2, OCSL and the proposed Mergers, based on the June 30, 2022 financial statements of each company. Representatives of Houlihan Lokey discussed certain considerations in connection with the proposed Mergers as well as the potential benefits of the Mergers (as identified by Oaktree). Representatives of Houlihan Lokey observed that, based on Oaktree’s assumptions underlying the Mergers, Oaktree expected the Mergers to be accretive to OCSL’s net investment income per share. Following this discussion with Houlihan Lokey, representatives of Oaktree discussed the financial model for the proposed Mergers, highlighting certain immaterial updates and noting the overall financial benefits of the transaction to OCSL remained unchanged. After the representatives of Oaktree and EY exited the meeting, Kirkland and Stradley discussed the updated draft of the Merger Agreement with the OCSL Special Committee, including a summary of the items that were still being negotiated, and the expected timeline for executing the agreement. The OCSL Special Committee discussed the Merger Agreement and the proposed Mergers, and Kirkland and Stradley answered questions from the OCSL Special Committee.

Later on August 29, 2022, Kirkland circulated a revised draft of the Merger Agreement to the OCSL Special Committee and Stradley.

On August 30, 2022, Stradley confirmed they did not have any further comments on the then current draft of the Merger Agreement and directed Kirkland to provide the draft to Sullivan & Cromwell. Later on August 30, 2022, Kirkland circulated a revised draft of the Merger Agreement to Sullivan & Cromwell, and Sullivan & Cromwell circulated the revised draft of the Merger Agreement to the OSI2 Special Committee.

On August 31, 2022, the OSI2 Special Committee held a special telephonic and video meeting, with representatives of Oaktree, KBW and Sullivan & Cromwell also in attendance at the request of the OSI2 Special Committee. KBW reviewed and discussed with the OSI2 Special Committee financial matters regarding OSI2, OCSL and the Liquidity Alternatives (including the proposed Mergers). Representatives of KBW discussed certain considerations in connection with the various Liquidity Alternatives, including the potential benefits of the Mergers (as identified by Oaktree). Following this discussion with KBW, representatives of Oaktree discussed an updated financial model for the proposed Mergers, highlighting material changes since the previously provided financial model. After the representatives of Oaktree exited the meeting, the OSI2 Special Committee discussed the financial matters reviewed by KBW, and representatives from KBW answered questions from the OSI2 Special Committee relating to the OSI2 Special Committee’s consideration of the different Liquidity Alternatives. The OSI2 Special Committee also discussed the latest draft of the Merger Agreement and representatives of Sullivan & Cromwell answered questions from the OSI2 Special Committee.

On September 1, 2022, representatives of Sullivan & Cromwell and Kirkland had a telephone conference to discuss the draft Merger Agreement.

On September 2, 2022, Sullivan & Cromwell circulated a revised draft the Merger Agreement to the OSI2 Special Committee, along with an outline of proposed responses to certain open points remaining in the draft, including the proposed approach for the termination fee, to which the OSI2 Special Committee expressed their agreement and confirmed they did not have any further comments on the then current draft of the Merger Agreement, recognizing that certain open points remained for discussion.

On September 3, 2022, Sullivan & Cromwell provided additional comments to Kirkland on the draft Merger Agreement, including the OSI2 Special Committee’s proposal for the termination fee to be payable by third parties to OCSL or OSI2 under certain circumstances.

On September 4, 2022, Kirkland circulated a revised draft of the Merger Agreement, which included the OSI2 Special Committee’s proposal for the termination fee, to the OCSL Special Committee and Stradley. From

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September 4, 2022 through September 6, 2022, the OCSL Special Committee and Stradley corresponded with Kirkland regarding the most recent changes to the Merger Agreement and confirmed agreement with the proposed termination fee and other terms of the Merger Agreement and authorized Kirkland to finalize the Merger Agreement.

On September 6, 2022, representatives of Sullivan & Cromwell and Kirkland had a telephone conference to discuss the Merger Agreement.

On September 8, 2022, Kirkland circulated a revised draft of the Merger Agreement to Sullivan & Cromwell. Also on September 8, 2022, representatives of Sullivan & Cromwell and Kirkland had a telephone conference to discuss the Merger Agreement.

On September 9, 2022, Sullivan & Cromwell provided additional comments on the draft Merger Agreement and representatives of Sullivan & Cromwell and Kirkland had a telephone call to discuss certain provisions of the Merger Agreement. Also on September 9, 2022, Kirkland circulated a revised draft of the Merger Agreement to Sullivan & Cromwell, and Sullivan & Cromwell circulated the revised draft of the Merger Agreement to the OSI2 Special Committee. On September 10, 2022, the OSI2 Special Committee confirmed they did not have any further comments on the then current draft of the Merger Agreement, recognizing that certain open points remained for discussion.

Later on September 10, 2022, the draft Merger Agreement was circulated to the OCSL Special Committee in advance of the OCSL Special Committee’s scheduled special telephonic and video meeting.

On September 13, 2022, Sullivan & Cromwell circulated a revised draft of the Merger Agreement to the OSI2 Special Committee, and Sullivan & Cromwell and the OSI2 Special Committee exchanged correspondence regarding the draft Merger Agreement. Also on September 13, 2022, Sullivan & Cromwell circulated a revised draft of the Merger Agreement to Kirkland.

On September 14, 2022, the OSI2 Special Committee held a special telephonic and video meeting, with representatives of Oaktree, Sullivan & Cromwell and KBW also participating in such meeting at the request of the OSI2 Special Committee. Representatives of Oaktree reviewed with the OSI2 Special Committee the key benefits that Oaktree expected to accrue to OSI2 and the OSI2 Stockholders as a result of the Mergers, including increased scale and access to secondary market liquidity for OSI2 Stockholders, reduced operating expense rates due to a larger asset base, seamless portfolio integration due to overlap in portfolios, an enhanced portfolio size and diversification with limited execution risk with the same investment adviser, advantages relative to other alternatives, the potential for improved access to debt capital markets and reduced financing costs, and the expectation of being accretive to OSI2 Stockholders. Representatives of Oaktree also discussed with the OSI2 Special Committee the potential risks of the Mergers, including the ability to obtain the required vote, potential pressure on OCSL’s Common Stock price and potential stockholder litigation. Oaktree representatives noted that, in order to maintain its RIC status and avoid paying excise taxes, OSI2 would be required to distribute all previously undistributed taxable income immediately prior to closing of the Mergers, which would reduce its NAV for determining the Exchange Ratio. Representatives of Oaktree then described the expected valuation process for determining the NAVs of OCSL and OSI2 within 48 hours of closing in order to calculate the Exchange Ratio. Representatives of Sullivan & Cromwell then discussed with the OSI2 Special Committee the findings required for the Mergers to qualify for an exemption to the joint transaction restrictions applicable to Business Development Companies under Section 57 of the Investment Company Act found in Rule 17a-8 of the Investment Company Act, which permits mergers of Business Development Companies with certain affiliates that would otherwise be prohibited by Section 57 of the Investment Company Act. At the request of the OSI2 Special Committee, KBW then reviewed and discussed the financial aspects of the proposed Mergers, including financial analyses performed by KBW, and rendered an opinion to the OSI2 Special Committee and, at the request of the OSI2 Special Committee, the OSI2 Board to the effect that, as of such date and subject to the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review

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undertaken by KBW as set forth in such opinion, the Exchange Ratio in the proposed Merger was fair, from a financial point of view, to the holders of OSI2 Common Stock.

The representatives of Oaktree then exited the meeting and, following a discussion of the foregoing matters and other matters presented, the OSI2 Special Committee (1) unanimously determined, and recommended that the OSI2 Board determine, (a) that the Merger Agreement, the Mergers and the other transactions contemplated by the Merger Agreement are advisable and in the best interests of OSI2 and the OSI2 Stockholders and (b) that the interests of existing OSI2 Stockholders would not be diluted for purposes of Rule 17a-8 of the Investment Company Act as a result of the transactions contemplated by the Merger Agreement, including the Mergers and (2) unanimously recommended that the OSI2 Board approve the Merger Agreement and the transactions contemplated thereby, including the Mergers.

On September 14, 2022, following completion of the meeting of the OSI2 Special Committee, the OSI2 Board (including Ms. Gero) held a special telephonic and video meeting, with representatives of Oaktree, Sullivan & Cromwell and KBW also in attendance at the request of the OSI2 Special Committee. The OSI2 Board reviewed the recommendation of the OSI2 Special Committee with Sullivan & Cromwell. Representatives of Sullivan & Cromwell then discussed with the OSI2 Board the findings required for the Mergers to qualify for an exemption to the joint transaction restrictions applicable to Business Development Companies under Section 57 of the Investment Company Act found in Rule 17a-8 of the Investment Company Act, which permits mergers of Business Development Companies with certain affiliates that would otherwise be prohibited by Section 57 of the Investment Company Act. Representatives from Oaktree and Sullivan & Cromwell then discussed with the OSI2 Board the draft Merger Agreement, the timing of the announcement of the Mergers and the process of soliciting the necessary OSI2 Stockholder and OCSL Stockholder approvals.

Thereafter, on the unanimous recommendation of the OSI2 Special Committee, the OSI2 Board, including a majority of the Independent Directors, unanimously (1) determined that (a) the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Mergers, are advisable and in the best interests of OSI2 and OSI2 Stockholders, and (b) that the interests of existing OSI2 Stockholders would not be diluted for purposes of Rule 17a-8 of the Investment Company Act as a result of the transactions contemplated by the Merger Agreement, including the Mergers, and (2) approved, adopted and declared advisable the Merger Agreement and the transactions contemplated thereby, including the Mergers. The OSI2 Board then directed that the Merger Agreement be submitted to OSI2 Stockholders for approval and resolved to recommend that OSI2 Stockholders vote to adopt the same and approve the Mergers.

Also on September 14, 2022, the OCSL Special Committee held a special telephonic and video meeting. Representatives of Oaktree, EY, Stradley, Kirkland and Houlihan Lokey also participated at the invitation of the OCSL Special Committee. Representatives of Oaktree discussed with the OCSL Special Committee the financial model for the Mergers, highlighting certain immaterial updates and noting the overall financial benefits of the transaction to OCSL remained unchanged. At the request of the OCSL Special Committee, Houlihan Lokey then reviewed and discussed its financial analyses with respect to OCSL, OSI2 and the proposed Mergers. Thereafter, at the request of the OCSL Special Committee, Houlihan Lokey orally rendered its opinion to the OCSL Special Committee (which was subsequently confirmed in writing by delivery of Houlihan Lokey’s written opinion dated September 14, 2022 addressed to the OCSL Special Committee and, as requested by the OCSL Special Committee, the OCSL Board) as to, as of such date, the fairness of the Exchange Ratio provided for in the Merger pursuant to the Merger Agreement, from a financial point of view, to OCSL.

The representatives of Oaktree and EY then exited the meeting. Representatives of Stradley then discussed with the OCSL Special Committee the findings required for the Mergers to qualify for an exemption to the joint transaction restrictions applicable to Business Development Companies under Section 57 of the Investment Company Act found in Rule 17a-8 of the Investment Company Act, which permits mergers of Business Development Companies with certain affiliates that would otherwise be prohibited by Section 57 of the Investment Company Act. Following a discussion of the matters presented at the meeting, the OCSL Special

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Committee (1) unanimously determined, and recommended that the OCSL Board determine, (a) that the Merger Agreement, the Mergers and the other transactions contemplated by the Merger Agreement are advisable and in the best interests of OCSL and the OCSL Stockholders and (b) that the interests of existing OCSL Stockholders would not be diluted for purposes of Rule 17a-8 of the Investment Company Act as a result of the transactions contemplated by the Merger Agreement, including the Mergers and (2) unanimously recommended that the OCSL Board approve the Merger Agreement and the transactions contemplated thereby, including the Mergers.

On September 14, 2022, following completion of the meeting of the OCSL Special Committee, the OCSL Board (including Ms. Gero) held a special telephonic and video meeting, with representatives of Oaktree, EY, Stradley, Kirkland and Houlihan Lokey also in attendance. The OCSL Board reviewed the recommendation of the OCSL Special Committee with Kirkland and Stradley. Representatives of Stradley then reviewed with the OCSL Board the findings required for the Mergers to qualify for an exemption to the joint transaction restrictions applicable to Business Development Companies under Section 57 of the Investment Company Act found in Rule 17a-8 of the Investment Company Act. Representatives from Oaktree and Kirkland then discussed with the OCSL Board the draft Merger Agreement, the timing of the announcement of the Mergers and the process of soliciting the necessary OCSL Stockholder and OSI2 Stockholder approvals.

Thereafter, on the unanimous recommendation of the OCSL Special Committee, the OCSL Board unanimously (1) determined that (a) the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Mergers, are advisable and in the best interests of OCSL and OCSL Stockholders, and (b) that the interests of existing OCSL Stockholders would not be diluted for purposes of Rule 17a-8 of the Investment Company Act as a result of the transactions contemplated by the Merger Agreement, including the Mergers and (2) approved, adopted and declared advisable the Merger Agreement and the transactions contemplated thereby, including the Mergers and the issuance of OCSL Common Stock pursuant to the Merger Agreement. The OCSL Board then directed that issuance of OCSL Common Stock pursuant to the Merger Agreement be submitted to OCSL Stockholders for approval and resolved to recommend that OCSL Stockholders vote to approve the same.

Following the September 14, 2022 meetings of the OSI2 Special Committee, the OSI2 Board, the OCSL Special Committee and the OCSL Board, OSI2, OCSL, Merger Sub and Oaktree executed and delivered the Merger Agreement. On September 15, 2022, OCSL and OSI2 issued a joint press release announcing the execution of the Merger Agreement and OCSL held an investor call to discuss the Mergers.

For more information concerning the terms and provisions of the Merger Agreement as negotiated by the parties, see “Description of the Merger Agreement” beginning on page 82 of this joint proxy statement/prospectus.

Reasons for the Mergers

OCSL

At various telephonic and video meetings, the OCSL Special Committee and the OCSL Board considered the approval of the Mergers and the Merger Agreement. In connection with their consideration, Oaktree provided the OCSL Special Committee and the OCSL Board with information regarding the proposed Mergers, OSI2 and the anticipated effects of the Mergers on OCSL and OCSL Stockholders. During the process of reviewing the materials and information provided and considering the Mergers, the OCSL Special Committee and the OCSL Board consulted with Stradley, Kirkland and Houlihan Lokey, as well as management of Oaktree. The OCSL Special Committee and the OCSL Board considered the nature and adequacy of the information provided, the terms of the Merger Agreement, their duties under state and federal law in considering and ultimately approving the Merger Agreement and the Mergers and the conflicts of interest presented by the transactions provided for in the Merger Agreement. The OCSL Special Committee and the OCSL Board considered numerous factors, including the ones described below, in connection with their consideration and approval of the Merger

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Agreement and the Mergers. On September 14, 2022, the OCSL Board and the OCSL Special Committee unanimously determined that the Mergers are in the best interests of OCSL and in the best interests of OCSL Stockholders, and that existing OCSL Stockholders will not suffer any dilution for purposes of Rule 17a-8 of the Investment Company Act as a result of the Mergers.

In considering the Mergers, the OCSL Special Committee reviewed comparative information about OCSL and OSI2 including, among other items: (1) their respective investment objectives, strategies, policies and restrictions and what changes, if any, would occur as a result of the Mergers; (2) their individual holdings, including, in particular, the extent of the overlap between the portfolios of OCSL and OSI2; (3) their existing leverage facilities; (4) their investment performance and financial results; (5) the anticipated effect of the Mergers on future OCSL net investment income, distributions and expenses; and (6) the U.S. federal income tax implications of the Mergers. In addition, the OCSL Special Committee reviewed comprehensive information regarding the anticipated benefits and possible risks to OCSL as a result of the Mergers, and the anticipated investment, market and financial synergies to be experienced by the combined company. The OCSL Special Committee considered the potential financial impacts to OCSL as a result of the Mergers in consultation with Houlihan Lokey, the financial advisor to the OCSL Special Committee.

The OCSL Special Committee and the OCSL Board, with the assistance of their legal and financial advisors, weighed various benefits and risks in considering the Mergers, both with respect to the immediate effects of the Mergers on OCSL and OCSL Stockholders and with respect to the potential benefits that could be experienced by the combined company after the Mergers. Some of the material factors considered by the OCSL Special Committee and the OCSL Board that assisted it in concluding that the Mergers are in the best interests of OCSL and OCSL Stockholders included, among others:

Expected Accretion to Net Investment Income. The OCSL Special Committee and the OCSL Board considered that the Mergers are expected to be accretive to net investment income, as a result of expense savings (as described more fully below) and the ability to operate at a slightly higher debt-to-equity ratio. In the short term, accretion to net investment income is also expected to result from the waiver of base management fees by Oaktree.

Increase in First Lien Investments. The OCSL Special Committee and the OCSL Board considered that, as of June 30, 2022, 84% of OSI2’s investment portfolio at fair value was in first lien senior secured loans, compared to 70% of OCSL’s investment portfolio. Based on the June 30, 2022 portfolio of each of OCSL and OSI2, on a pro forma basis, 73% of the portfolio of the combined entity would be in first lien senior secured loans. The OCSL Special Committee and the OCSL Board considered the lower risk profile of the OCSL portfolio post-Mergers due to a larger percentage of first lien loans.

Expected Greater Access to Debt Capital. The OCSL Special Committee and the OCSL Board discussed how the larger scale of the combined company may improve OCSL’s access to more diverse and lower cost sources of debt capital compared to what OCSL would be expected to obtain without the scale provided by the Mergers. The OCSL Special Committee and the OCSL Board noted that the larger size of the combined company could also allow for OCSL to operate at a slightly higher debt-to-equity ratio given the larger size and diversification.

Increased Scale and Improved Secondary Market Liquidity. The OCSL Special Committee and the OCSL Board considered scale and liquidity advantages expected to accrue to the combined company as a result of its larger size. The OCSL Special Committee and the OCSL Board considered that larger Business Development Companies tend to have higher average daily trading volumes, which would give existing OCSL Stockholders more flexibility to manage their investments and would be expected to attract new investors, including institutional investors, seeking a more liquid stock than OCSL provides on a standalone basis. The OCSL Special Committee and the OCSL Board also considered that larger Business Development Companies generally have broader coverage by equity research analysts, which is also expected to expand the potential stockholder base of

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the combined company. The OCSL Special Committee and the OCSL Board noted that increased interest in OCSL Common Stock by a larger number of potential stockholders could result in increased trading volumes and higher trading prices, which could provide greater flexibility and opportunity to raise additional equity capital in the future.

Acquisition of a Known, Diversified Portfolio. The OCSL Special Committee and the OCSL Board considered that the significant overlap of OSI2’s investments with those of OCSL (approximately 97% of the investments held by OSI2 on June 30, 2022 were also held by OCSL) and Oaktree’s familiarity with the investments held by OSI2, which would outweigh considerations related to slightly increased portfolio concentration, would result in a more straightforward and faster integration of the portfolio into OCSL’s than a portfolio of a third party. The OCSL Special Committee and the OCSL Board noted that the acquisition of OSI2’s portfolio of investments would lead to a larger portfolio with strong credit quality, as no investments were on non-accrual as of June 30, 2022. The OCSL Special Committee and the OCSL Board also considered the advantages to OCSL of immediately acquiring known, income-producing assets already diligenced and managed by Oaktree as opposed to the process of raising incremental capital in follow-on equity or rights offerings, and suffering lower returns until such capital is invested in income producing assets consistent with Oaktree’s underwriting standards. The OCSL Special Committee and the OCSL Board also considered that execution and integration risk could be lower as compared to a merger with an unaffiliated entity.

No Dilution for Purposes of Rule 17a-8 of the Investment Company Act. The OCSL Special Committee and the OCSL Board considered that the Exchange Ratio (and thus the number of shares of OCSL Common Stock to be issued to OSI2 Stockholders pursuant to the Merger Agreement) will be determined on a NAV-for-NAV basis (determined shortly before the Closing Date on the basis of methodologies that were considered and approved by the OCSL Board) and therefore the interests of the OCSL Stockholders will not be diluted for purposes of Rule 17a-8 under the Investment Company Act as a result of the Mergers.

Potential for Expense Savings. The OCSL Special Committee and the OCSL Board also considered that, as a result of the Mergers, certain redundant professional services and other corporate expenses would be eliminated, which would reduce the potential expenses of the combined company as compared to the aggregate expenses of OCSL and OSI2 on a standalone basis. In addition, the OCSL Special Committee considered that the combined company may have access to lower-cost sources of capital and thus be able to reduce its interest expense. The OCSL Special Committee and the OCSL Board noted that, although certain one-time costs would be borne by OCSL Stockholders in connection with the Mergers, such costs would be offset by the base management fee waiver by Oaktree and operating expense synergies.

Opinion of Houlihan Lokey, Financial Advisor to the OCSL Special Committee. The OCSL Special Committee considered the financial analysis reviewed by Houlihan Lokey with the OCSL Special Committee as well as the oral opinion of Houlihan Lokey rendered to the OCSL Special Committee on September 14, 2022 (which was subsequently confirmed in writing by delivery of Houlihan Lokey’s written opinion dated September 14, 2022 addressed to the OCSL Special Committee and, as requested by the OCSL Special Committee, the OCSL Board), as to, as of September 14, 2022, the fairness of the Exchange Ratio provided for in the Merger pursuant to the Merger Agreement, from a financial point of view, to OCSL, as more fully described below in the section entitled “ — Opinion of the Financial Advisor to the OCSL Special Committee.”

Tax Consequences of the Mergers. The OCSL Special Committee and the OCSL Board considered that the Mergers are expected to qualify as a “reorganization” within the meaning of Section 368(a) of the Code. The Mergers are anticipated to be treated as a tax-free reorganization for U.S. federal income tax purposes and OCSL Stockholders are not expected to recognize any gain or loss for U.S. federal income tax purposes as a result of the Mergers.

Other Considerations. The OCSL Special Committee and the OCSL Board noted that the Mergers are not expected to affect the ability of OCSL to comply with its regulatory obligations, including its ability to continue

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to operate in compliance with the asset coverage requirements set forth in the Investment Company Act and to pay dividends required of RICs.

In the course of its deliberations, the OCSL Board and the OCSL Special Committee also considered a variety of risks and other potentially negative factors that could cause the Mergers not to close or the anticipated benefits of the Mergers not to be realized, including the following (which are not in any relative order of importance):

This discussion of the information and factors that the OCSL Special Committee and the OCSL Board considered in making their decisions is not intended to be exhaustive but includes the material benefits, risks and other factors considered by the OCSL Special Committee and the OCSL Board. Because of the wide variety of factors considered in connection with the evaluation of the Mergers and Merger Agreement and the complexity of those matters, the OCSL Board and the OCSL Special Committee did not find it useful to, and did not attempt to, quantify, rank or otherwise assign relative weights to these factors. In addition, the individual members of the OCSL Special Committee and the OCSL Board may have given different weights to different factors.

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The OCSL Special Committee consulted with Houlihan Lokey, as its financial advisor, in connection with its evaluation of the financial terms of the Mergers. In addition, the OCSL Special Committee and the OCSL Board relied on their respective legal advisors for legal analysis in connection with the transactions contemplated by the Merger Agreement, including the Mergers.

The OCSL Special Committee and, upon the unanimous recommendation of the OCSL Special Committee, the OCSL Board considered all of these factors and others as a whole and, on balance, determined the Mergers to be in the best interests of OCSL and OCSL Stockholders and unanimously approved the Mergers and the Merger Agreement.

OSI2

At various telephonic and video meetings, the OSI2 Special Committee and the OSI2 Board considered the approval of the Mergers and the Merger Agreement. In connection with their consideration, Oaktree provided the OSI2 Special Committee and the OSI2 Board with information regarding the proposed Mergers, OCSL and the anticipated effects of the Mergers on OSI2 and OSI2 Stockholders. Throughout the process of reviewing the materials and information provided and considering the Liquidity Alternatives, including the Mergers, the OSI2 Special Committee and the OSI2 Board consulted with Sullivan & Cromwell and KBW, as well as management of Oaktree. The OSI2 Special Committee and the OSI2 Board considered the nature and adequacy of the information provided, the terms of the Merger Agreement, their duties under state and federal law in considering and ultimately approving the Merger Agreement and the Mergers and the conflicts of interest presented by the transactions provided for in the Merger Agreement. The OSI2 Special Committee and the OSI2 Board considered numerous factors, including the ones described below, in connection with their consideration and approval of the Merger Agreement and the Mergers. On September 14, 2022, the OSI2 Board and the OSI2 Special Committee unanimously determined that the Mergers are advisable and in the best interests of OSI2, and that existing OSI2 Stockholders will not suffer any dilution for purposes of Rule 17a-8 of the Investment Company Act as a result of the Mergers.

In considering the Mergers, the OSI2 Special Committee and the OSI2 Board reviewed comparative information about OSI2 and OCSL including, among other items: (1) their respective investment objectives, strategies, policies and restrictions and what changes would occur as a result of the Mergers; (2) information about how their holdings substantially overlap and differ; (3) their existing leverage facilities; (4) their short-term and long-term investment performance history and financial results; (5) the level of past distributions and expenses and the anticipated effect of the Mergers on future net investment income, distributions and expenses; (6) their respective investment advisory agreements and expense ratios; and (7) the U.S. federal income tax implications of the Mergers. In addition, the OSI2 Special Committee and the OSI2 Board reviewed comprehensive information regarding the anticipated benefits and possible risks to OSI2 and OSI2 Stockholders as a result of the Mergers, and the anticipated investment, market and financial synergies to be experienced by the combined company. The OSI2 Special Committee also considered financial aspects of the proposed Mergers in consultation with KBW, the financial advisor to the OSI2 Special Committee.

The OSI2 Special Committee and the OSI2 Board weighed various benefits and risks in considering the Mergers, both with respect to the immediate effects of the Mergers on OSI2 and OSI2 Stockholders and with respect to the potential benefits that could be experienced by the combined company after the Mergers. Some of the material factors considered by the OSI2 Special Committee and the OSI2 Board that assisted it in concluding that the Mergers are in the best interests of OSI2 and OSI2 Stockholders included, among others:

Expected Accretion to Net Investment Income. The OSI2 Special Committee and the OSI2 Board considered that the Mergers are expected to be accretive to net investment income in both the short-term and long-term. The OSI2 Special Committee and the OSI2 Board noted that Oaktree expects, in the short term, accretion to net investment income to be delivered primarily by the waiver of base management fees by Oaktree and, over the long term, by expense savings through operational synergies and a streamlined capital structure.

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Expected Greater Access to Debt Capital. The OSI2 Special Committee and the OSI2 Board considered how OCSL’s larger scale may improve access to more diverse, lower cost sources of capital. The OSI2 Board also considered that OSI2 Stockholders may benefit from OCSL’s lower cost, more flexible capital structure, including investment grade credit ratings and unsecured debt.

Immediate Access to Liquidity. The OSI2 Special Committee and the OSI2 Board considered that upon completion of the Mergers OSI2 Stockholders will receive OCSL Common Stock that is listed on Nasdaq and is freely saleable, providing immediate access to liquidity. The OSI2 Special Committee and OSI2 Board also considered alternative paths to liquidity for OSI2 Stockholders but determined the potential benefits of the proposed Mergers represent a superior alternative for OSI2 Stockholders.

Similarities in Investment Strategies and Risks. The OSI2 Special Committee and OSI2 Board reviewed the investment objectives and strategies of OCSL and noted the similarities to the objectives and strategies of OSI2 and substantially similar risks and that each focuses on direct lending to middle-market companies. The OSI2 Special Committee and OSI2 Board took into consideration that OSI2 and OCSL are each managed by Oaktree and, after the Mergers, OSI2 Stockholders would be invested in a similarly structured investment vehicle and that their investment experience would likely be comparable in the combined entity.

Broader Equity Coverage and Improved Secondary Market Liquidity. In the Mergers, OSI2 Stockholders will receive OCSL Common Stock and the assets of OSI2 will be incorporated into OCSL, increasing OCSL’s market capitalization and NAV. The OSI2 Special Committee and the OSI2 Board considered that larger Business Development Companies tend to have higher average daily trading volumes, which would give existing OSI2 Stockholders more flexibility to manage their investments and would be expected to attract new investors seeking a more liquid stock than either company provides on a standalone basis. The OSI2 Board and the OSI2 Special Committee noted that OCSL’s increased size as a result of the Mergers could result in additional market coverage of OCSL by analysts and, potentially, an increased focus by institutional investors on the combined company. The OSI2 Special Committee and the OSI2 Board noted that increased interest in the OCSL Common Stock by a larger number of potential stockholders could result in increased trading volumes and higher trading prices, which could provide greater flexibility for the combined company to raise additional equity capital in the future.

Expected Dividend Accretion. The OSI2 Special Committee and the OSI2 Board considered that the Mergers would be accretive to dividends received by OSI2 Stockholders in both the short-term and long-term, as OSI2 Stockholders would benefit from the higher yielding assets currently in the OCSL portfolio.

Continuity of Oaktree and the Management Team. The OSI2 Special Committee and the OSI2 Board, considered that the combined company would have the same investment adviser and management team that have already been considered and approved by the OSI2 Board. The OSI2 Special Committee and the OSI2 Board considered that, because there would be no change in the investment adviser, the combined entity and the OSI2 Stockholders would be expected to receive the same nature, quality and extent of services from Oaktree that they are currently receiving and would continue to benefit from the experience and expertise of its current management team, including familiarity with the investment portfolio.

Ease of Portfolio Integration. The OSI2 Special Committee and the OSI2 Board considered that the significant overlap of OSI2’s investments with those of OCSL (approximately 97% of the investments held by OSI2 on June 30, 2022 were also held by OCSL) and Oaktree’s familiarity with the investments held by OSI2 would result a more straightforward and faster integration of OSI2’s portfolio into that of OCSL than into a portfolio of an unaffiliated acquirer with reduced execution risk. The OSI2 Special Committee and the OSI2 Board also considered the larger portfolio size and increased number of individual borrowers of the combined entity.

Potential for Operational Synergies via the Elimination of Redundant Expenses. The OSI2 Special Committee and the OSI2 Board also considered that, as a result of the Mergers, certain redundant professional

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services and other corporate expenses would be eliminated, which would reduce the potential expenses of the combined company as compared to the aggregate expenses of OCSL and OSI2 on a standalone basis. The OSI2 Special Committee and the OSI2 Board noted that, although certain one-time costs would be borne by OSI2 Stockholders in connection with the Mergers, such costs would be offset by the OCSL base management fee waiver and operating expense synergies.

Tax Consequences of the Mergers. The OSI2 Special Committee and the OSI2 Board considered that the Mergers are expected to qualify as a “reorganization” within the meaning of Section 368(a) of the Code. OSI2 Stockholders are not expected to recognize any gain or loss for U.S. federal income tax purposes on the exchange of shares of OSI2 Common Stock for shares of OCSL Common Stock pursuant to the Mergers, except with respect to cash received in lieu of fractional shares of OCSL Common Stock. OSI2 Stockholders will receive a distribution of their proportionate share of OSI2’s undistributed net investment income and net realized gains, if any, prior to or shortly after the completion of the Mergers (the “OSI2 Distribution”) that generally will be taxable to taxable stockholders for U.S. federal, state and local income tax purposes. The OSI2 Distribution may include return of capital which would generally result in a reduction in basis.

No Dilution for Purposes of Rule 17a-8 of the Investment Company Act. The OSI2 Special Committee and the OSI2 Board considered that the Exchange Ratio (and thus the number of shares of OCSL Common Stock to be issued to OSI2 Stockholders pursuant to the Merger Agreement) will be determined on a NAV-for-NAV basis (determined shortly before the Closing Date on the basis of methodologies that were considered and approved by the OSI2 Board), supporting a determination that the interests of the OSI2 Stockholders will not be diluted for purposes of Rule 17a-8 under the Investment Company Act as a result of the Mergers.

Opinion of KBW, Financial Advisor to the OSI2 Special Committee. The OSI2 Special Committee considered the financial presentation, dated September 14, 2022, of KBW provided to and reviewed with the OSI2 Special Committee and the opinion, dated September 14, 2022, of KBW to the OSI2 Special Committee and OSI2 Board as to, as of the date of the opinion, the fairness, from a financial point of view, to the holders of OSI2 Common Stock of the Exchange Ratio in the Merger, as more fully described below in the section entitled “ — Opinion of the Financial Advisor to the OSI2 Special Committee.” At the request of the OSI2 Special Committee, KBW also attended the special telephonic and video meeting of the OSI2 Board following the delivery of its opinion to provide the OSI2 Board with the opportunity to discuss KBW’s opinion.

Other Considerations. The OSI2 Special Committee and the OSI2 Board also considered that the OSI2 Board will declare the OSI2 Distribution.

In the course of its deliberations, the OSI2 Board and the OSI2 Special Committee also considered a variety of risks and other potentially negative factors, including the following (which are not in any relative order of importance):

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This discussion of the information and factors that the OSI2 Special Committee and the OSI2 Board considered in making their decisions is not intended to be exhaustive, but includes the material benefits, risks and other factors considered by the OSI2 Special Committee and the OSI2 Board. Because of the wide variety of factors considered in connection with the evaluation of the Mergers and Merger Agreement and the complexity of those matters, the OSI2 Board and the OSI2 Special Committee did not find it useful to, and did not attempt to, quantify, rank or otherwise assign relative weights to these factors. In addition, the individual members of the OSI2 Special Committee and the OSI2 Board may have given different weights to different factors.

The OSI2 Special Committee consulted with KBW, as its financial advisor regarding financial matters, in connection with the OSI2 Special Committee’s evaluation of the Liquidity Alternatives, including the financial terms of the Mergers. In addition, the OSI2 Special Committee and the OSI2 Board relied on their legal advisors for legal analysis in connection with the transactions contemplated by the Merger Agreement, including the Mergers.

The OSI2 Special Committee and, upon the unanimous recommendation of the OSI2 Special Committee, the OSI2 Board considered all of these factors and others as a whole and, on balance, determined the Mergers to be in the best interests of OSI2 and OSI2 Stockholders and unanimously approved the Mergers and the Merger Agreement.

OCSL Board Recommendation

The OCSL Board, upon recommendation of the OCSL Special Committee, has unanimously approved the Merger Agreement, including the Mergers and the related transactions, and the proposed issuance of OCSL Common Stock in connection with the Mergers, and directed that the proposed issuance of OCSL Common Stock in connection with the Mergers be submitted to the OCSL Stockholders for approval at the OCSL Annual Meeting. The OCSL Board unanimously recommends that OCSL Stockholders vote “FOR” the Merger Stock Issuance Proposal.

OSI2 Board Recommendation

The OSI2 Board, upon recommendation of the OSI2 Special Committee, has unanimously approved the Merger Agreement, including the Mergers and the related transactions, and directed that the Merger Agreement be submitted to the OSI2 Stockholders for approval at the OSI2 Special Meeting. The OSI2 Board unanimously recommends that OSI2 Stockholders vote “FOR” the Merger Proposal.

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Certain Prospective Financial Information Provided by Oaktree

Neither OCSL nor OSI2 (or Oaktree on their behalf), as a matter of course, makes public long-term projections as to their respective future investment income, net investment income or other results due to, among other reasons, the inherent uncertainty of the underlying assumptions and estimates. However, Oaktree prepared certain unaudited forecasted financial information, which was made available to the OCSL Special Committee and the OCSL Board in connection with their evaluation of the proposed Mergers and to Houlihan Lokey who was authorized and directed to use and rely upon such information for purposes of providing financial advice to the OCSL Special Committee. In addition, Oaktree prepared certain unaudited forecasted financial information, which was made available to the OSI2 Special Committee and the OSI2 Board in connection with their evaluation of the Liquidity Alternatives, including the proposed Mergers, and to KBW who was authorized and directed to use and rely upon such information for purposes of providing financial advice to the OSI2 Special Committee. The prospective financial information contained in this joint proxy statement/prospectus was prepared for internal use and not with a view to public disclosure and is being included in this joint proxy statement/prospectus only because the prospective financial information was provided to the OCSL Special Committee and OSI2 Special Committee in connection with their evaluation of the proposed Mergers or to Houlihan Lokey and KBW who were authorized and directed to use and rely upon such information for purposes of providing financial advice to the OCSL Special Committee and the OSI2 Special Committee, respectively. The summary of the projections and prospective financial information included in this joint proxy statement/prospectus are not being provided to influence the decision of OCSL Stockholders to vote for the Merger Stock Issuance Proposal or OSI2 Stockholders to vote for the Merger Proposal.

The prospective financial information was not prepared with a view to compliance with the published guidelines of the SEC or the guidelines established by the American Institute of Certified Public Accountants for preparation and presentation of prospective financial information. The prospective financial information does not purport to present operations in accordance with U.S. generally accepted accounting principles, and OCSL’s and OSI2’s registered public accounting firms have not examined, compiled or otherwise applied procedures to the prospective financial information and accordingly assume no responsibility for such information.

The prospective financial information provided by Oaktree on behalf of OCSL and OSI2, as applicable, was based solely on the information available to Oaktree management at that time. The inclusion of the prospective financial information in this joint proxy statement/prospectus should not be regarded as an indication that the prospective financial information will be necessarily predictive of actual future results, and the forecasts should not be relied upon as such. None of OCSL, OSI2, Oaktree or any other person makes any representation to any security holders regarding the ultimate performance of OCSL or OSI2, as applicable, compared to the prospective financial information set forth in this joint proxy statement/prospectus.

The prospective financial information is not fact and reflects numerous assumptions and estimates as to future events made by Oaktree management of OCSL or OSI2, as applicable, that were believed to be reasonable at the time the prospective financial information was prepared and other factors such as industry performance and general business, economic, regulatory, market and financial conditions, as well as factors specific to the businesses of OCSL and OSI2, all of which are difficult to predict and many of which are beyond the control of OCSL and OSI2. Other persons attempting to project the future results of OCSL and OSI2 will make their own assumptions that could result in projections materially different than those presented in this joint proxy statement/prospectus. In addition, the prospective financial information does not take into account any circumstances or events occurring after the date that they were prepared. Further, the prospective financial information does not take into account the effect of any failure to occur of the Mergers. Accordingly, there can be no assurance that the prospective financial information will be realized, and actual results could vary significantly from those reflected in the prospective financial information.

Neither OCSL nor OSI2 intends to update or otherwise revise the prospective financial information to reflect circumstances existing after the date when made or to reflect the occurrence of future events even in the

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event that any or all of the assumptions underlying the prospective financial information are shown to be in error. The projections and prospective financial information in this joint proxy statement/prospectus are forward-looking statements. These statements involve certain risks and uncertainties that could cause actual results to differ materially from those in the forward-looking statements. See “Special Note Regarding Forward-Looking Statements.”

Oaktree made available to OCSL and Houlihan Lokey (who was authorized and directed to use and rely upon such information for purposes of providing financial advice to the OCSL Special Committee) the following information with respect to:

In addition, Oaktree made available to OSI2 and KBW (which was authorized and directed to use and rely upon the following information for purposes of providing financial advice to the OSI2 Special Committee) the following information:

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Opinion of the Financial Advisor to the OCSL Special Committee

On September 14, 2022, Houlihan Lokey orally rendered its opinion to the OCSL Special Committee (which was subsequently confirmed in writing by delivery of Houlihan Lokey’s written opinion addressed to the OCSL Special Committee and the OCSL Board dated September 14, 2022), as to, as of September 14, 2022, the fairness of the Exchange Ratio provided for in the Merger pursuant to the Merger Agreement, from a financial point of view, to OCSL.

Houlihan Lokey’s opinion was directed to the OCSL Special Committee (in its capacity as such) and, as requested by the OCSL Special Committee, the OCSL Board (in its capacity as such), and only addressed the fairness of the Exchange Ratio provided for in the Merger pursuant to the Merger Agreement, from a financial point of view, to OCSL and did not address any other aspect or implication of the Merger or any other agreement, arrangement or understanding entered into in connection therewith or otherwise. The summary of Houlihan Lokey’s opinion in this joint proxy statement/prospectus is qualified in its entirety by reference to the full text of its written opinion, which is attached as Annex B to this joint proxy statement/prospectus and describes the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered by Houlihan Lokey in connection with the preparation of its opinion. However, neither Houlihan Lokey’s opinion nor the summary of its opinion and the related analyses set forth in this joint proxy statement/prospectus are intended to be, and do not constitute, advice or a recommendation to the OCSL Special Committee, the OCSL Board, any security holder of OCSL or any other person as to how to act or vote with respect to any matter relating to the Merger.

In arriving at its opinion, Houlihan Lokey made such reviews, analyses and inquiries as it deemed necessary and appropriate under the circumstances. Among other things, Houlihan Lokey:

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Houlihan Lokey relied upon and assumed, without independent verification, the accuracy and completeness of all data, material and other information furnished, or otherwise made available, to it, discussed with or reviewed by it, or publicly available, and did not assume any responsibility with respect to such data, material and other information. In addition, management of Oaktree advised Houlihan Lokey, and Houlihan Lokey assumed, that (a) the OSI2 Projections, the OSI2 Liquidation Projections, and the OSI2 IPO Projections were reasonably prepared in good faith on bases reflecting the best currently available estimates and judgments of such management as to the future financial results and condition of OSI2 on a going concern basis, under a wind-down and liquidation, and following an IPO, respectively, and (b) the OCSL Projections and the Pro Forma OCSL Projections were reasonably prepared in good faith on bases reflecting the best currently available estimates and judgments of such management as to the future financial results and condition of OCSL on a standalone basis and after giving effect to the Merger, respectively. At the OCSL Special Committee’s direction, Houlihan Lokey assumed that the OSI2 Projections and the OCSL Projections provided a reasonable basis on which to evaluate OSI2, OCSL and the Merger and Houlihan Lokey, at the OCSL Special Committee’s direction, used and relied upon the OSI2 Projections and the OCSL Projections for purposes of its analyses and opinion. Houlihan Lokey expressed no view or opinion with respect to the OSI2 Projections, the OSI2 Liquidation Projections, the OSI2 IPO Projections, the OCSL Projections, the Pro Forma OCSL Projections or the respective assumptions on which they were based. Houlihan Lokey relied upon and assumed, without independent verification, that there had been no change in the business, assets, liabilities, financial condition, results of operations, cash flows or prospects of OSI2 or OCSL since the respective dates of the most recent financial statements and other information, financial or otherwise, provided to it that would be material to its analyses or opinion, and that there was no information or any facts that would make any of the information reviewed by it incomplete or misleading.

Houlihan Lokey relied upon and assumed, without independent verification, that (a) the representations and warranties of all parties to the Merger Agreement and all other related documents and instruments referred to therein were true and correct, (b) each party to the Merger Agreement and such other related documents and instruments would fully and timely perform all of the covenants and agreements required to be performed by such party, (c) all conditions to the consummation of the Merger would be satisfied without waiver thereof, and (d) the Merger would be consummated in a timely manner in accordance with the terms described in the Merger Agreement and such other related documents and instruments, without any amendments or modifications thereto that would be material to its analyses or opinion. Houlihan Lokey also assumed that the Merger, together with the Second Merger, would qualify, for federal income tax purposes, as a “reorganization” within the meaning of Section 368(a) of the Code. Houlihan Lokey relied upon and assumed, without independent verification, that

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(i) the Merger would be consummated in a manner that complies in all respects with all applicable federal and state statutes, rules and regulations, and (ii) all governmental, regulatory, and other consents and approvals necessary for the consummation of the Merger would be obtained and that no delay, limitations, restrictions or conditions would be imposed or amendments, modifications or waivers made that would result in the disposition of any assets of OSI2 or OCSL, or otherwise have an effect on the Merger, OSI2 or OCSL or any expected benefits of the Merger that would be material to its analyses or opinion. In addition, Houlihan Lokey relied upon and assumed, without independent verification, that the final form of the Merger Agreement would not differ from the draft of the Merger Agreement identified above in any respect material to its analyses or opinion.

Furthermore, in connection with its opinion, Houlihan Lokey was not requested to, and did not, make any physical inspection or independent appraisal or evaluation of any of the assets, properties or liabilities (fixed, contingent, derivative, off-balance-sheet or otherwise) of OSI2, OCSL or any other party. Houlihan Lokey did not estimate, and expressed no opinion regarding, the liquidation value of any entity or business. Houlihan Lokey did not undertake any independent analysis of any potential or actual litigation, regulatory action, possible unasserted claims or other contingent liabilities, to which OSI2 or OCSL was or may have been a party or was or may have been subject, or of any governmental investigation of any possible unasserted claims or other contingent liabilities to which OSI2 or OCSL was or may have been a party or was or may have been subject.

Houlihan Lokey was not requested to, and did not, (a) solicit any indications of interest from third parties with respect to the Merger, the securities, assets, businesses or operations of OSI2, OCSL or any other party, or any alternatives to the Merger, or (b) advise the OCSL Special Committee, the OCSL Board or any other party with respect to alternatives to the Merger. Houlihan Lokey’s opinion was necessarily based on financial, economic, market and other conditions as in effect on, and the information made available to Houlihan Lokey as of, the date of its opinion. As the OCSL Special Committee was aware the credit, financial and stock markets had been experiencing unusual volatility and Houlihan Lokey expressed no opinion or view as to any potential effects of such volatility on the Merger, and Houlihan Lokey’s opinion did not purport to address potential developments in any such markets. Houlihan Lokey did not undertake, and is under no obligation, to update, revise, reaffirm or withdraw its opinion, or otherwise comment on or consider events occurring or coming to its attention after the date of its opinion. Houlihan Lokey did not express any opinion as to what the value of OCSL Common Stock actually would be when issued pursuant to the Merger or the price or range of prices at which OSI2 Common Stock or OCSL Common Stock may be purchased or sold, or otherwise be transferable, at any time. Houlihan Lokey assumed that the shares of OCSL Common Stock to be issued in the Merger to holders of OSI2 Common Stock would be listed on Nasdaq immediately following the consummation of the Merger.

Houlihan Lokey’s opinion was furnished for the use of the OCSL Special Committee and the OCSL Board (each in its capacity as such) in connection with its evaluation of the Merger and may not be used for any other purpose without Houlihan Lokey’s prior written consent. Houlihan Lokey’s opinion was not intended to be, and does not constitute, a recommendation to the OCSL Special Committee, the OCSL Board, any security holder or any other party as to how to act or vote with respect to any matter relating to the Merger or otherwise.

Houlihan Lokey’s opinion only addressed the fairness of the Exchange Ratio provided for in the Merger pursuant to the Merger Agreement, from a financial point of view, to OCSL and did not address any other aspect or implication of the Merger, any related transaction or any agreement, arrangement or understanding entered into in connection therewith or otherwise, including, without limitation, the termination of the OSI2 Advisory Agreement and the OSI2 Administration Agreement immediately after the Effective Time and immediately prior to the Second Merger, or the Second Merger. Houlihan Lokey was not requested to opine as to, and its opinion did not express an opinion as to or otherwise address, among other things: (i) the underlying business decision of the OCSL Special Committee, the OCSL Board, OCSL, its security holders or any other party to proceed with or effect the Merger, (ii) the terms of any arrangements, understandings, agreements or documents related to, or the form, structure or any other portion or aspect of, the Merger or otherwise (other than the Exchange Ratio to the extent expressly specified in its opinion), (iii) the fairness of any portion or aspect of the Merger to the holders of any class of securities, creditors or other constituencies of OCSL, or to any other party, except if and only to the

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extent expressly set forth in the last sentence of Houlihan Lokey’s opinion, (iv) the relative merits of the Merger as compared to any alternative business strategies or transactions that might have been available for OCSL, OSI2 or any other party, (v) the fairness of any portion or aspect of the Merger to any one class or group of OCSL’s or any other party’s security holders or other constituents vis-à-vis any other class or group of OCSL’s or such other party’s security holders or other constituents (including, without limitation, the allocation of any consideration amongst or within such classes or groups of security holders or other constituents), (vi) the appropriate capital structure of OCSL, whether OCSL should be issuing debt or equity securities or a combination of both in the Merger, or the form, structure or any aspect or terms of any debt or equity financing for the Merger or the likelihood of obtaining such financing, (vii) whether or not OCSL, OSI2, their respective security holders or any other party is receiving or paying reasonably equivalent value in the Merger, (viii) the solvency, creditworthiness or fair value of OCSL, OSI2 or any other participant in the Merger, or any of their respective assets, under any applicable laws relating to bankruptcy, insolvency, fraudulent conveyance or similar matters, or (ix) the fairness, financial or otherwise, of the amount, nature or any other aspect of any compensation to or consideration payable to or received by any officers, directors or employees of any party to the Merger, any class of such persons or any other party, relative to the Exchange Ratio or otherwise. Furthermore, Houlihan Lokey did not express any opinion, counsel or interpretation regarding matters that require legal, regulatory, accounting, insurance, tax or other similar professional advice. Houlihan Lokey assumed that such opinions, counsel or interpretations had been or would be obtained from the appropriate professional sources. Furthermore, Houlihan Lokey relied, with the consent of the OCSL Special Committee, on the assessments by the OCSL Special Committee, the OCSL Board, OCSL and their respective advisors, as to all legal, regulatory, accounting, insurance and tax matters with respect to OSI2, OCSL and the Merger or otherwise.

In preparing its opinion to the OCSL Special Committee, Houlihan Lokey performed a variety of analyses, including those described below. The summary of Houlihan Lokey’s analyses is not a complete description of the analyses underlying Houlihan Lokey’s opinion. The preparation of such an opinion is a complex process involving various quantitative and qualitative judgments and determinations with respect to the financial, comparative and other analytical methods employed and the adaptation and application of these methods to the unique facts and circumstances presented. As a consequence, neither Houlihan Lokey’s opinion nor its underlying analyses is readily susceptible to summary description. Houlihan Lokey arrived at its opinion based on the results of all analyses undertaken by it and assessed as a whole and did not draw, in isolation, conclusions from or with regard to any individual analysis, methodology or factor. While the results of each analysis were taken into account in reaching Houlihan Lokey’s overall conclusion with respect to fairness, Houlihan Lokey did not make separate or quantifiable judgments regarding individual analyses. Accordingly, Houlihan Lokey believes that its analyses and the following summary must be considered as a whole and that selecting portions of its analyses, methodologies and factors, without considering all analyses, methodologies and factors, could create a misleading or incomplete view of the processes underlying Houlihan Lokey’s analyses and opinion.

In performing its analyses, Houlihan Lokey considered general business, economic, industry and market conditions, financial and otherwise, and other matters as they existed on, and could be evaluated as of, the date of its opinion. No company, transaction or business used in Houlihan Lokey’s analyses for comparative purposes is identical to OCSL, OSI2 or the proposed Merger and an evaluation of the results of those analyses is not entirely mathematical. The estimates contained in the OCSL Projections and the OSI2 Projections and the implied exchange ratio reference ranges indicated by Houlihan Lokey’s analyses are not necessarily indicative of actual values or predictive of future results or values, which may be significantly more or less favorable than those suggested by the analyses. In addition, any analyses relating to the value of assets, businesses or securities do not purport to be appraisals or to reflect the prices at which businesses or securities actually may be sold, which may depend on a variety of factors, many of which are beyond the control of OCSL and OSI2. Much of the information used in, and accordingly the results of, Houlihan Lokey’s analyses are inherently subject to substantial uncertainty.

Houlihan Lokey’s opinion was only one of many factors considered by the OCSL Special Committee and the OCSL Board in evaluating the proposed Merger. Neither Houlihan Lokey’s opinion nor its analyses were

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determinative of the Merger Consideration or of the views of the OCSL Special Committee or the OCSL Board with respect to the Merger or the Merger Consideration. The type and amount of consideration payable in the Merger were determined through negotiation between OCSL and OSI2, and the decision to enter into the Merger Agreement was solely that of the OCSL Special Committee and the OCSL Board.

Material Financial Analyses

The following is a summary of the material financial analyses performed by Houlihan Lokey in connection with the preparation of its opinion and reviewed with the OCSL Special Committee on September 14, 2022. The order of the analyses does not represent relative importance or weight given to those analyses by Houlihan Lokey. The analyses summarized below include information presented in tabular format. The tables alone do not constitute a complete description of the analyses. Considering the data in the tables below without considering the full narrative description of the analyses, as well as the methodologies underlying, and the assumptions, qualifications and limitations affecting, each analysis, could create a misleading or incomplete view of Houlihan Lokey’s analyses.

For purposes of its analyses, Houlihan Lokey reviewed the Adjusted June 30, 2022 NAVs of OCSL and OSI2, prepared and provided to Houlihan Lokey by Oaktree, and compared the implied exchange ratio, determined on the basis of the Adjusted June 30 NAVs, of 2.7037 shares of OCSL Common Stock for each share of OSI2 Common Stock to the relative value reference ranges that Houlihan Lokey believed were indicated by its financial analyses of OCSL and OSI2.

For purposes of its analyses, Houlihan Lokey reviewed a number of financial metrics, including:

Unless the context indicates otherwise, share prices used in the selected companies analysis described below were based on the closing price of the common stock of the selected companies listed below as of September 8, 2022, and transaction values for the selected transactions analysis described below were calculated on an equity value basis based on the announced transaction equity price and other public information available at the time of the announcement. The estimates of future financial performance of OCSL relied upon for the financial analyses described below were based on the OCSL Projections, and the estimates of future financial performance of OSI2 relied upon for the financial analyses described below were based on the OSI2 Projections. The estimates of the future financial performance of the selected companies listed below were based on publicly available research analyst estimates for those companies.

Selected Companies Analysis. Houlihan Lokey reviewed certain financial data for selected companies with publicly traded equity securities that Houlihan Lokey deemed relevant. The financial data reviewed included:

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With respect to OCSL, the selected companies and resulting high, mean, median and low financial data were:

With respect to OSI2, the selected companies and resulting high, mean, median and low financial data were:

OCSL. Taking into account the results of the selected companies analysis, Houlihan Lokey applied selected ranges of 8.50x to 10.50x to OCSL’s estimated Price-to-CY 2022E Net Investment Income Per Share, 8.00x to 10.00x to OCSL’s estimated Price-to-CY 2023E Net Investment Income Per Share, 10.50% to 8.50% to OCSL’s Last Quarter Annualized Dividend Per Share and 0.90x to 1.05x to OCSL’s NAV Per Share.

OSI2. Taking into account the results of the selected companies analysis, Houlihan Lokey applied selected ranges of 8.50x to 10.50x to OSI2’s estimated Price-to-CY 2022E Net Investment Income Per Share, 8.00x to 10.00x to OSI2’s estimated Price-to-CY 2023E Net Investment Income Per Share, 11.00% to 9.00% to OSI2’s Last Quarter Annualized Dividend Per Share and 0.90x to 1.00x to OSI2’s NAV Per Share.

The selected companies analysis indicated implied exchange ratio reference ranges of 1.8882 to 2.8813 shares of OCSL Common Stock for each share of OSI2 Common Stock based on estimated Price-to-CY 2022E

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Net Investment Income Per Share, 1.8824 to 2.9412 shares of OCSL Common Stock for each share of OSI2 Common Stock based on estimated Price-to-CY 2023E Net Investment Income Per Share, 2.0000 to 3.0196 shares of OCSL Common Stock for each share of OSI2 Common Stock based on Last Quarter Annualized Dividend Per Share and 2.3250 to 3.0138 shares of OCSL Common Stock for each share of OSI2 Common Stock based on NAV Per Share, in each case as compared to the implied exchange ratio of 2.7037 shares of OCSL Common Stock for each share of OSI2 Common Stock based on the Adjusted June 30, 2022 NAVs of OCSL and OSI2.

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Selected Transactions Analysis. Houlihan Lokey considered certain financial terms of certain transactions involving target companies that Houlihan Lokey deemed relevant. The financial data reviewed included transaction value as a multiple of NAV Per Share, and the selected transactions and resulting high, mean, median and low financial data were:

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Taking into account the results of the selected transactions analysis, Houlihan Lokey applied a selected multiple range of 0.90x to 1.00x to OCSL’s NAV Per Share and 0.90x to 1.00x to OSI2’s NAV Per Share. The selected transactions analysis indicated an implied exchange ratio reference range of 2.4412 to 3.0138 shares of OCSL Common Stock for each share of OSI2 Common Stock, as compared to the implied exchange ratio of 2.7037 shares of OCSL Common Stock for each share of OSI2 Common Stock based on the Adjusted June 30, 2022 NAVs of OCSL and OSI2.

Discounted Dividend Analysis. Houlihan Lokey performed a discounted dividend analysis of OCSL and OSI2 based on the OCSL Projections and the OSI2 Projections, respectively. With respect to OCSL, Houlihan Lokey applied a range of terminal value multiples of 0.90x to 1.00x to OCSL’s estimated 2026E NAV and discount rates ranging from 8.5% to 10.5%. With respect to OSI2, Houlihan Lokey applied a range of terminal value multiples of 0.90x to 1.00x to OSI2’s estimated 2026E NAV and discount rates ranging from 9.0% to 11.0%. The discounted dividend analysis indicated an implied exchange ratio reference range of 2.2543 to 2.9458 shares of OCSL Common Stock for each share of OSI2 Common Stock, as compared to the implied exchange ratio of 2.7037 shares of OCSL Common Stock for each share of OSI2 Common Stock based on the Adjusted June 30, 2022 NAVs of OCSL and OSI2.

Other Matters

Houlihan Lokey was engaged by the OCSL Special Committee to act as its financial advisor in connection with a possible merger, consolidation, business combination, sale or other similar transaction involving OCSL and OSI2. The OCSL Special Committee engaged Houlihan Lokey based on Houlihan Lokey’s experience and reputation. Houlihan Lokey is regularly engaged to provide financial advisory services in connection with mergers and acquisitions, financings, and financial restructurings. Pursuant to its engagement by the OCSL Special Committee, Houlihan Lokey is entitled to a transaction fee of $1,000,000, of which $50,000 became payable to Houlihan Lokey upon its engagement as the OCSL Special Committee’s financial advisor, $300,000 became payable to Houlihan Lokey upon the rendering of its opinion to the OCSL Special Committee and the remainder is contingent upon the consummation of the Merger. OCSL also agreed to reimburse Houlihan Lokey for certain expenses and to indemnify Houlihan Lokey, its affiliates and certain related parties against certain liabilities and expenses arising out of or relating to Houlihan Lokey’s engagement.

In the ordinary course of business, certain of Houlihan Lokey’s employees and affiliates, as well as investment funds in which they may have financial interests or with which they may co-invest, may acquire, hold or sell, long or short positions, or trade, in debt, equity, and other securities and financial instruments (including loans and other obligations) of, or investments in, OSI2, OCSL, or any other party that may be involved in the Merger and their respective affiliates or security holders or any currency or commodity that may be involved in the Merger.

Houlihan Lokey and/or certain of its affiliates have in the past provided and are currently providing financial advisory and/or other services to OCSL and have in the past provided and are currently providing investment banking, financial advisory and/or other financial or consulting services to OCM, or one or more security holders or affiliates of, and/or portfolio companies of investment funds affiliated or associated with, OCM (collectively, with OCM, the “OCM Group”), for which Houlihan Lokey and its affiliates have received, and may receive, compensation, including, among other things, during the prior two years (i) having provided

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and currently providing valuation advisory services for financial reporting purposes to OCSL, (ii) having acted as financial advisor to the special committee of the board of directors of OCSI, then managed by Oaktree, in connection with the OCSI Merger, which closed in March 2021, (iii) having acted as financial advisor to a noteholder group, of which one or more members of the Oaktree Group were members, in relation to their interests as noteholders of Frontier Communications Corporation in connection with its chapter 11 bankruptcy proceedings, which concluded in April 2021, (iv) having acted as financial advisor to a consortium of shareholders, in which OCM was a leading member along with Centerbridge Partners, LP, in connection with the restructuring and reorganization of Garrett Motion, Inc., which was completed in April 2021, and (v) having acted as financial advisor to a lender group, of which one or more members of the Oaktree Group were members, in relation to their interests as lenders to Array Canada, Inc. in connection with its refinancing transaction, which closed in September 2021, for which Houlihan Lokey received aggregate compensation of approximately $35 million. Houlihan Lokey and certain of its affiliates may provide investment banking, financial advisory and/or other financial or consulting services to OSI2, OCSL, members of the Oaktree Group, other participants in the Merger or certain of their respective affiliates or security holders in the future, for which Houlihan Lokey and its affiliates may receive compensation. In addition, Houlihan Lokey and certain of its affiliates and certain of Houlihan Lokey’s and their respective employees may have committed to invest in private equity or other investment funds managed or advised by OCM, other participants in the Merger or certain of their respective affiliates or security holders, and in portfolio companies of such funds, and may have co-invested with the members of the Oaktree Group, other participants in the Merger or certain of their respective affiliates or security holders, and may do so in the future. Furthermore, in connection with bankruptcies, restructurings, distressed situations and similar matters, Houlihan Lokey and certain of its affiliates may have in the past acted, may currently be acting and may in the future act as financial advisor to debtors, creditors, equity holders, trustees, agents and other interested parties (including, without limitation, formal and informal committees or groups of creditors) that may have included or represented and may include or represent, directly or indirectly, or may be or have been adverse to, OSI2, OCSL, members of the Oaktree Group, other participants in the Merger or certain of their respective affiliates or security holders, for which advice and services Houlihan Lokey and its affiliates have received and may receive compensation.

Opinion of the Financial Advisor to the OSI2 Special Committee

OSI2 engaged KBW to render financial advisory and investment banking services to the OSI2 Special Committee, including an opinion to the OSI2 Special Committee and, as requested by the OSI2 Special Committee, the OSI2 Board, as to the fairness, from a financial point of view, to the holders of OSI2 Common Stock of the Exchange Ratio in the proposed Merger. OSI2 selected KBW because KBW is a nationally recognized investment banking firm with substantial experience in transactions similar to the Mergers. As part of its investment banking business, KBW is regularly engaged in the valuation of business development company securities in connection with mergers and acquisitions.

As part of its engagement, representatives of KBW attended the meetings of the OSI2 Special Committee and the OSI2 Board held on September 14, 2022 at which the OSI2 Special Committee and the OSI2 Board evaluated the proposed Mergers. At the meeting of the OSI2 Special Committee, KBW reviewed the financial aspects of the proposed Mergers and rendered an opinion to the OSI2 Special Committee and the OSI2 Board to the effect that, as of such date and subject to the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by KBW as set forth in such opinion, the Exchange Ratio in the proposed Merger was fair, from a financial point of view, to the holders of OSI2 Common Stock. The OSI2 Board, upon recommendation of the OSI2 Special Committee, approved the Merger Agreement at its meeting.

The description of the opinion set forth herein is qualified in its entirety by reference to the full text of the opinion, which is attached as Annex C to this document and is incorporated herein by reference, and describes the procedures followed, assumptions made, matters considered, and qualifications and limitations on the review undertaken by KBW in preparing the opinion.

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KBW’s opinion speaks only as of the date of the opinion. The opinion was for the information of, and was directed to, the OSI2 Special Committee (in its capacity as such) and, as requested by the OSI2 Special Committee, the OSI2 Board (in its capacity as such) in connection with their respective consideration of the financial terms of the Mergers. The opinion addressed only the fairness, from a financial point of view, of the Exchange Ratio in the Merger to the holders of OSI2 Common Stock. It did not address the underlying business decision of OSI2 to engage in the Mergers or enter into the Merger Agreement or constitute a recommendation to the OSI2 Special Committee or the OSI2 Board in connection with the Mergers, and it does not constitute a recommendation to any holder of OSI2 Common Stock or any stockholder of any other entity as to how to vote or act in connection with the Mergers or any other matter, nor does it constitute a recommendation as to whether or not any such stockholder should enter into a voting, stockholders’, affiliates’ or other agreement with respect to the Mergers or exercise any dissenters’ or appraisal rights that may be available to such stockholder.

KBW’s opinion was reviewed and approved by KBW’s Fairness Opinion Committee in conformity with its policies and procedures established under the requirements of Rule 5150 of the Financial Industry Regulatory Authority.

At the direction of OSI2 and without independent verification, KBW relied upon and assumed for purposes of its analyses and opinion, that the OSI2 Per Share NAV and the OCSL Per Share NAV would be $18.58 and $6.87, respectively, and that, as a result thereof, the Exchange Ratio would be 2.7037x.

In connection with the opinion, KBW reviewed, analyzed and relied upon material bearing upon the financial and operating condition of OSI2 and OCSL and bearing upon the Mergers, including, among other things:

KBW’s consideration of financial information and other factors that it deemed appropriate under the circumstances or relevant to its analyses included, among others, the following:

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KBW also performed such other studies and analyses as it considered appropriate and took into account its assessment of general economic, market and financial conditions and its experience in other transactions, as well as its experience in securities valuation and knowledge of the business development company industry generally. KBW also participated in discussions with Oaktree management regarding the past and current business operations, regulatory relations, financial condition and future prospects of OSI2 and OCSL and such other matters as KBW deemed relevant to its inquiry. KBW was not requested to assist, and did not assist, OSI2 with soliciting indications of interest from third parties regarding a potential transaction with OSI2.

In conducting its review and arriving at its opinion, KBW relied upon and assumed the accuracy and completeness of all of the financial and other information provided to or discussed with KBW or that was publicly available and did not independently verify the accuracy or completeness of any such information or assume any responsibility or liability for such verification, accuracy or completeness. KBW relied, with the consent of OSI2 and the OSI2 Special Committee, upon Oaktree management, as to the reasonableness and achievability of the financial and operating forecasts and projections of OSI2 and OCSL and the estimates regarding certain pro forma financial effects of the Mergers on OCSL (including, without limitation, the cost savings, related expenses and operating synergies expected to result or be derived from the Mergers), all as referred to above (and the assumptions and bases for all such information), and KBW assumed that all such information was reasonably prepared and represented the best currently available estimates and judgments of Oaktree management and that the forecasts, projections and estimates reflected in such information would be realized in the amounts and in the time periods estimated by such management.

It is understood that the foregoing financial information of OSI2 and OCSL that was provided to KBW was not prepared with the expectation of public disclosure and that all of the foregoing financial information was based on numerous variables and assumptions that are inherently uncertain (including, without limitation, factors related to general economic and competitive conditions and, in particular, the widespread disruption, extraordinary uncertainty and unusual volatility arising from global tensions and political unrest, economic uncertainty, inflation, and the COVID-19 pandemic, including the effect of evolving governmental interventions and non-interventions) and, accordingly, actual results could vary significantly from those set forth in such information. KBW assumed, based on discussions with Oaktree management, and with the consent of OSI2 and the OSI2 Special Committee, that all such information provided a reasonable basis upon which KBW could form its opinion, and KBW expressed no view as to any such information or the assumptions or bases therefor. Among other things, such information assumed that the ongoing COVID-19 pandemic could have an adverse impact, which was assumed to be limited, on OSI2 and OCSL. KBW relied on all such information without independent verification or analysis and did not in any respect assume any responsibility or liability for the accuracy or completeness thereof.

KBW also assumed that there were no material changes in the assets, liabilities, financial condition, results of operations, business or prospects of either OSI2 or OCSL since the date of the last financial statements of each

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such entity that were made available to KBW. In rendering its opinion, KBW did not make or obtain any evaluations or appraisals or physical inspection of the property, assets or liabilities (contingent or otherwise) of OSI2 or OCSL, the collateral securing any of such assets or liabilities, or the collectability of any such assets, nor did KBW examine any individual loan or credit files, nor did it evaluate the solvency, financial capability or fair value of OSI2 or OCSL under any state or federal laws, including those relating to bankruptcy, insolvency or other matters. Estimates of values of companies and assets do not purport to be appraisals or necessarily reflect the prices at which companies or assets may actually be sold. Such estimates are inherently subject to uncertainty and should not be taken as KBW’s view of the actual value of any companies or assets.

KBW assumed, in all respects material to its analyses, the following:

KBW assumed that the Mergers would be consummated in a manner that complies with the applicable provisions of the Securities Act, the Exchange Act, and all other applicable federal and state statutes, rules and regulations. KBW was further advised by representatives of OSI2 that OSI2 relied upon advice from its advisors (other than KBW) or other appropriate sources as to all legal, financial reporting, tax, accounting and regulatory matters with respect to OSI2, OCSL, Merger Sub, the Mergers and any related transaction, and the Merger Agreement. KBW did not provide advice with respect to any such matters.

KBW’s opinion addressed only the fairness, from a financial point of view, as of the date of such opinion, of the Exchange Ratio in the Merger to the holders of OSI2 Common Stock. KBW expressed no view or opinion as to any other terms or aspects of the Mergers or any term or aspect of any related transaction (including the termination of the OSI2 Investment Advisory Agreement and the OSI2 Administration Agreement and the fee waiver to be entered into by and between OCSL and Oaktree), including without limitation, the form or structure of the Mergers or any such related transaction, any consequences of the Mergers or any related transaction to OSI2, its stockholders, creditors or otherwise, or any terms, aspects, merits or implications of any employment, consulting, voting, support, stockholder or other agreements, arrangements or understandings contemplated or entered into in connection with the Mergers, any such related transaction, or otherwise. KBW’s opinion was necessarily based upon conditions as they existed and could be evaluated on the date of the opinion and the information made available to KBW through the date of the opinion. There has been significant volatility in the stock and other financial markets arising from global tensions, economic uncertainty and the effects of the

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COVID-19 pandemic, including the effect of evolving governmental interventions and non-interventions. Developments subsequent to the date of KBW’s opinion may have affected and may affect the conclusion reached in KBW’s opinion and KBW did not and does not have an obligation to update, revise or reaffirm its opinion. KBW expressed no view or opinion as to any changes to the OSI2 Per Share NAV or the OCSL Per Share NAV after the date of its opinion from the respective amounts thereof that KBW was directed to assume for purposes of its analyses and opinion. KBW’s opinion did not address, and KBW expressed no view or opinion with respect to:

In performing its analyses, KBW made numerous assumptions with respect to industry performance, general business, economic, market and financial conditions and other matters, which are beyond the control of KBW, OSI2 and OCSL. Any estimates contained in the analyses performed by KBW are not necessarily indicative of actual values or future results, which may be significantly more or less favorable than suggested by these analyses. Additionally, estimates of the value of businesses or securities do not purport to be appraisals or to reflect the prices at which such businesses or securities might actually be sold. Accordingly, these analyses and estimates are inherently subject to substantial uncertainty. In addition, the KBW opinion was among several factors taken into consideration by the OSI2 Special Committee in making its determination to recommend the approval by the OSI2 Board of the Merger Agreement and the Mergers and by the OSI2 Board in making its determination to approve the Merger Agreement and the Mergers. Consequently, the analyses described below should not be viewed as determinative of the decision of OSI2 Special Committee or the OSI2 Board with respect to the fairness of the Exchange Ratio. The type and amount of consideration payable in the Merger were determined through negotiation between OSI2 and OCSL and the decision of OSI2 to enter into the Merger Agreement was solely that of the OSI2 Special Committee and the OSI2 Board.

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The following is a summary of the material financial analyses included in the presentation made by KBW and reviewed with the OSI2 Special Committee in connection with its opinion to the OSI2 Special Committee and the OSI2 Board. The summary is not a complete description of the financial analyses underlying the opinion or the presentation reviewed by KBW with the OSI2 Special Committee, but summarizes the material analyses performed and presented in connection with such opinion. The financial analyses summarized below include information presented in tabular format. The tables alone do not constitute a complete description of the financial analyses. The preparation of a fairness opinion is a complex analytic process involving various determinations as to appropriate and relevant methods of financial analysis and the application of those methods to the particular circumstances. Therefore, a fairness opinion is not readily susceptible to partial analysis or summary description. In arriving at its opinion, KBW did not attribute any particular weight to any analysis or factor that it considered, but rather made qualitative judgments as to the significance and relevance of each analysis and factor. Accordingly, KBW believes that its analyses and the summary of its analyses must be considered as a whole and that selecting portions of its analyses and factors or focusing on the information presented below in tabular format, without considering all analyses and factors or the full narrative description of the financial analyses, including the methodologies and assumptions underlying the analyses, could create a misleading or incomplete view of the process underlying its analyses and opinion.

Implied Transaction Value for the Mergers. KBW calculated an implied transaction value for the proposed Mergers of $18.25 per outstanding share of OSI2 common stock based on an assumed 2.7037x exchange ratio and the closing price of OCSL Common Stock on September 13, 2022. This implied transaction value for the proposed Mergers was used to calculate implied transaction multiples and those multiples were compared to the ranges of multiples found in the financial analyses described below. This implied transaction value for the proposed Mergers was also compared to the ranges of implied value per share of OSI2 Common Stock in the financial analyses described below.

Selected Companies Analysis of OSI2. Using publicly available information, KBW reviewed, among other things, the market performance of 23 selected publicly traded, externally managed business development companies with market capitalizations between $100 million and $1 billion. Growth/total return business development companies were excluded from the selected companies.

The selected companies were as follows (shown by column in descending order of market capitalization):

To perform this analysis, KBW used market price information as of September 13, 2022, reported NAV per share data as of the end of the most recent completed quarterly period available (which in the case of OSI2 was June 30, 2022) and most recent completed quarterly period available annualized (“MRQ annualized”) reported net investment income per share (“NII”). KBW also used calendar years 2022 and 2023 earnings per share estimates (“EPS”) taken from consensus “street estimates” of the selected companies.

KBW’s analysis showed the following concerning the market performance of the selected companies, as well as certain corresponding implied transaction multiples for the proposed Mergers based on the implied

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transaction value for the proposed Mergers of $18.25 per outstanding share of OSI2 Common Stock and using historical financial information for OSI2 as of and for the three-month period (annualized) ended June 30, 2022:

KBW then applied a range of price-to-NAV per share multiples of 0.81x to 0.97x derived from the 25^th percentile and 75^th percentile multiples of the selected companies to the June 30, 2022 NAV per share of OSI2, a range of price-to-MRQ annualized NII multiples of 8.69x to 10.40x derived from the 25^th percentile and 75^th percentile multiples of the selected companies to the MRQ annualized NII per share of OSI2 for the three-month period ended June 30, 2022, and a range of price-to-estimated calendar year 2023 EPS multiples of 8.16x to 10.00x derived from the 25^th percentile and 75^th percentile multiples of the selected companies to the calendar year 2023 EPS of OSI2, which was based on financial and operating forecasts and projections of OSI2 provided by Oaktree management. This analysis indicated the following ranges of the implied value per share of OSI2 Common Stock, as compared to the implied transaction value for the proposed Mergers of $18.25 per outstanding share of OSI2 Common Stock:

No company used as a comparison in the above selected companies analysis is identical to OSI2. Accordingly, an analysis of these results is not mathematical. Rather, it involves complex considerations and judgments concerning differences in financial and operating characteristics of the companies involved.

Selected Companies Analysis of OCSL. Using publicly available information, KBW compared, among other things, the market performance of OCSL to 14 selected publicly traded, externally managed business development companies with market capitalizations above $750 million.

The selected companies were as follows (shown by column in descending order of market capitalization):

To perform this analysis, KBW used market price information as of September 13, 2022 and reported NAV per share data as of the end of the most recent completed quarterly period available (which in the case of OCSL was June 30, 2022) and reported MRQ annualized NII. KBW also used calendar years 2022 and 2023 EPS estimates taken from consensus “street estimates” of OCSL and the selected companies.

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KBW’s analysis showed the following concerning the market performance of OCSL and the selected companies:

No company used as a comparison in the above selected companies analysis is identical to OCSL. Accordingly, an analysis of these results is not mathematical. Rather, it involves complex considerations and judgments concerning differences in financial and operating characteristics of the companies involved.

Selected Transactions Analysis. KBW reviewed publicly available information related to 20 selected acquisitions of U.S. business development companies announced since the beginning of 2009. Reverse mergers and distressed deals were excluded from the selected transactions.

The selected transactions were as follows:

For each selected transaction, KBW derived the following implied transaction statistics, in each case based on the transaction consideration value paid for the acquired company (including contributions by external managers) and using financial data based on the acquired company’s then latest publicly available financial statements prior to the announcement of the respective transaction (adjusted to reflect announced pre-closing adjustments):