Orion Office REIT Inc., a Maryland corporation (the “Company”) – Registration Statement filed with the Securities and Exchange Commission (the “Commission”) on the date hereof on Form S-3 (as amended from time to time, the “Registration Statement”) pertaining to the registration of the resale from time to time of up to 1,120,000 shares of common stock of the Company, par value $0.001 per share (“Common Stock”) issuable upon the exercise of certain Warrants (as defined below)

the corporate charter of the Company represented by Articles of Incorporation filed with the State Department of Assessments and Taxation of Maryland (the “Department”) on July 1, 2021 and Articles of Amendment and Restatement filed with the Department on November 10, 2021 (the “Charter”);

the Amended and Restated Bylaws of the Company, dated as of November 15, 2021(the “Bylaws”);

resolutions adopted by the Board of Directors, on or as of November 9, 2021, and November 1, 2022 (the “Directors’ Resolutions”);

the Registration Statement and the related base prospectus dated November 2, 2022 (the “Base Prospectus”), and the related prospectus supplement dated November 2, 2022 (the “Prospectus Supplement” and together with the Base Prospectus, the “Prospectus”);

a status certificate of the Department, dated as of a recent date, to the effect that the Company is duly incorporated and existing under the laws of the State of Maryland;

that certain Warrant to Purchase Shares, dated on or about November 12, 2021, issued to OAP Holdings, LLC, a Delaware limited liability company by the Company (the “OAP Warrant”), and that certain Warrant to Purchase Shares, dated on or about November 12, 2021, issued to Arch Street Capital Partners, LLC, a Delaware limited liability company, by the Company, (together with the OAP Warrant, collectively, the “Warrants”);

a certificate of Paul C. Hughes, General Counsel and Secretary of the Company, and Gavin B. Brandon, Chief Financial Officer, Executive Vice President and Treasurer of the Company, dated as of a recent date (the “Officers’ Certificate”), to the effect that, among other things, the copies of the Charter, the Bylaws, the Organizational Minutes, the Directors’ Resolutions and the Warrants are true, correct and complete, have not been rescinded or modified and are in full force and effect as of the date of the Officers’ Certificate, and certifying as to the manner of adoption of the Directors’ Resolutions; and

such other documents and matters as we have deemed necessary and appropriate to render the opinions set forth in this opinion letter, subject to the limitations, assumptions and qualifications noted below.

each person executing any of the Documents on behalf of any party (other than the Company) is duly authorized to do so;

each natural person executing any of the Documents is legally competent to do so;

any of the Documents submitted to us as originals are authentic; the form and content of any Documents submitted to us as unexecuted drafts do not differ in any respect relevant to this opinion from the form and content of such documents as executed and delivered; any of the Documents submitted to us as certified, facsimile or photostatic copies conform to the original Documents; all signatures on all of the Documents are genuine; all public records reviewed or relied upon by us or on our behalf are true and complete; all statements and information contained in the Documents are true and complete; there has been no modification of, or amendment to, any of the Documents, and there has been no waiver of any provision of any of the Documents by action or omission of the parties or otherwise;

the form of certificate, receipt or other instrument or document representing the Securities approved subsequent to the date hereof will conform in all respects to the requirements applicable under Maryland law;

none of the Shares will be issued or transferred in violation of the provisions of Article VI of the Charter relating to restrictions on ownership and transfer of shares of stock of the Company; and

upon the issuance of the Shares subsequent to the date hereof, the total number of shares of Common Stock issued and outstanding on the date subsequent to the date hereof on which the Shares are issued will not exceed the total number of shares of Common Stock that the Company is authorized to issue under the Charter.

The Company has been duly incorporated and is validly existing as a corporation in good standing under the laws of the State of Maryland.

The Shares have been duly authorized for issuance by all necessary corporate action on the part of the Company and when issued and delivered by the Company in accordance with the terms of the Warrants and payment of the exercise price therefor, as established under the terms of the Warrants, such Shares will be validly issued, fully paid and non-assessable.