Form of 3.700% Senior Note due 2021

Exhibit 4.1

Form of 3.700% Senior Note due 2021

THIS GLOBAL NOTE IS HELD BY THE DEPOSITORY (AS DEFINED IN THE SECOND SUPPLEMENTAL INDENTURE GOVERNING THIS NOTE) OR ITS NOMINEE IN CUSTODY FOR THE BENEFIT OF THE BENEFICIAL OWNERS HEREOF, AND IS NOT TRANSFERABLE TO ANY PERSON UNDER ANY CIRCUMSTANCES EXCEPT THAT (1) THE TRUSTEE MAY MAKE SUCH NOTATIONS HEREON AS MAY BE REQUIRED PURSUANT TO SECTION 1.6 OF THE SECOND SUPPLEMENTAL INDENTURE, (2) THIS GLOBAL NOTE MAY BE EXCHANGED IN WHOLE BUT NOT IN PART PURSUANT TO SECTION 1.6 OF THE SECOND SUPPLEMENTAL INDENTURE, (3) THIS GLOBAL NOTE MAY BE DELIVERED TO THE TRUSTEE FOR CANCELLATION PURSUANT TO SECTION 401 OF THE ORIGINAL INDENTURE AND (4) THIS GLOBAL NOTE MAY BE TRANSFERRED TO A SUCCESSOR DEPOSITORY WITH THE PRIOR WRITTEN CONSENT OF THE ISSUER.

UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR NOTES IN DEFINITIVE FORM, THIS NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITORY TO A NOMINEE OF THE DEPOSITORY OR BY A NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY OR ANOTHER NOMINEE OF THE DEPOSITORY OR BY THE DEPOSITORY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITORY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITORY.  UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) (“DTC”), TO THE ISSUER OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR SUCH OTHER NAME AS MAY BE REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO. OR SUCH OTHER ENTITY AS MAY BE REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

CORPORATE OFFICE PROPERTIES, L.P.

3.700% SENIOR NOTES DUE 2021

No. 001

CUSIP No.:                                 22003BAJ5

ISIN:                  US22003BAJ52

$300,000,000

Corporate Office Properties, L.P., a Delaware limited partnership (herein called the “Issuer,” which term includes any successor entity under the Indenture referred to on the reverse hereof), for value received hereby promises to pay to Cede & Co., or its registered assigns, the principal sum of THREE HUNDRED MILLION DOLLARS ($300,000,000), or such lesser amount as is set forth in the Schedule of Increases or Decreases In Note on the other side of this Note, on June 15, 2021 at the office or agency of the Issuer maintained for that purpose in accordance with the terms of the Indenture, in such coin or currency of the United States of America as at the time of payment shall be legal tender for the payment of public and private debts, and to pay interest, semi-annually on June 15 and December 15 of each year, commencing December 15, 2014, on said principal sum at said office or agency, in like coin or currency, at the rate per annum of 3.700%, from June 15 or December 15, as the case may be, next preceding the date of this Note to which interest has been paid or duly provided for, unless no interest has been paid or duly provided for on the Notes, in which case from May 21, 2014 until payment of said principal sum has been made or duly provided for.  The Issuer shall pay interest on any Notes in certificated form by check mailed to the address of the Person entitled thereto as it appears in the Note Register; provided, however, that a Holder of any Notes in certificated form in the aggregate principal amount of more than $2.0 million may specify by written notice to the Issuer that it pay interest by wire transfer of immediately available funds to the account specified by the Noteholder in such notice, or on any Global Note by wire transfer of immediately available funds to the account of the Depository or its nominee.

Reference is made to the further provisions of this Note set forth on the reverse hereof and the Indenture governing this Note.  Such further provisions shall for all purposes have the same effect as though fully set forth at this place.

This Note shall not be valid or become obligatory for any purpose until the certificate of authentication hereon shall have been signed manually or by facsimile or other electronic imaging means by the Trustee or a duly authorized authenticating agent under the Indenture.

IN WITNESS WHEREOF, the Issuer has caused this Note to be duly executed.

TRUSTEE’S CERTIFICATE OF AUTHENTICATION

This is one of the Notes described in the within-named Indenture.

REVERSE SIDE OF NOTE

Corporate Office Properties, L.P.

3.700% SENIOR NOTES DUE 2021

This Note is one of a duly authorized issue of Notes of the Issuer, designated as its 3.700% Senior Notes due 2021 (herein called the “Notes”), issued under and pursuant to an Indenture dated as of September 16, 2013 (herein called the “Original Indenture”), among the Issuer, Corporate Office Properties Trust, a Maryland real estate investment trust (the “Guarantor”), and U.S. Bank National Association, as trustee (herein called the “Trustee”), as supplemented by the Second Supplemental Indenture dated as of May 21, 2014 (herein called the “Second Supplemental Indenture,” and together with the Original Indenture, the “Indenture”), among the Issuer, the Guarantor and the Trustee, to which Indenture and any indentures supplemental thereto reference is hereby made for a description of the rights, limitations of rights, obligations, duties and immunities thereunder of the Trustee, the Issuer, the Guarantor and the Holders of the Notes.  Defined terms used but not otherwise defined in this Note shall have the respective meanings ascribed thereto in the Indenture.

If an Event of Default (other than an Event of Default specified in Section 501(5), 501(6) or 501(7) of the Original Indenture with respect to the Issuer) occurs and is continuing, the principal of, premium, if any, and accrued and unpaid interest on all Notes may be declared to be due and payable by either the Trustee or the Holders of at least twenty five percent (25%) in aggregate principal amount of the Notes then outstanding, and, upon said declaration the same shall be immediately due and payable.  If an Event of Default specified in Section 501(5), 501(6) or 501(7) of the Original Indenture occurs with respect to the Issuer, the principal of and premium, if any, and interest accrued and unpaid on all the Notes shall be immediately and automatically due and payable without necessity of further action.

The Indenture contains provisions permitting the Issuer and the Trustee, with the consent of the Holders of not less than a majority in aggregate principal amount of the Notes at the time outstanding, to execute supplemental indentures adding any provisions to or changing in any manner or eliminating any of the provisions of the Indenture or of any supplemental indenture or modifying in any manner the rights of the Holders of the Notes, subject to exceptions set forth in Section 902 of the Original Indenture.  Subject to the provisions of the Indenture, the Holders of not less than a majority in aggregate principal amount of the Notes at the time outstanding may, on behalf of the Holders of all of the Notes, waive any past Default or Event of Default, subject to exceptions set forth in the Indenture.

No reference herein to the Indenture and no provision of this Note or of the Indenture shall impair, as among the Issuer and the Holder of the Notes, the obligation of the Issuer, which is absolute and unconditional, to pay the principal of, premium, if any, on and interest on this Note at the place, at the respective times, at the rate and in the coin or currency herein and in the Indenture prescribed.

Interest on the Notes shall be computed on the basis of a 360-day year of twelve 30-day months.

The Notes are issuable in fully registered form, without coupons, in denominations of $2,000 principal amount and any multiple of $2,000.  At the office or agency of the Issuer referred to on the face hereof, and in the manner and subject to the limitations provided in the Indenture, without payment of any service charge but with payment of a sum sufficient to cover any tax, assessment or other governmental charge that may be imposed in connection with any registration or exchange of Notes, Notes may be exchanged for a like aggregate principal amount of Notes of any other authorized denominations.

The Issuer shall have the right to redeem the Notes under certain circumstances as set forth in Section 1.4(d), Section 1.4(e) and Section 1.4(f) of the Second Supplemental Indenture.

The Notes are not subject to redemption through the operation of any sinking fund.

Except as expressly provided in Article 16 of the Original Indenture, no recourse for the payment of the principal of or any premium or interest on this Note, or for any claim based hereon or otherwise in respect hereof, and no recourse under or upon any obligation, covenant or agreement of the Issuer in the Indenture or any supplemental indenture or in any Note, or because of the creation of any indebtedness represented thereby, shall be had against any incorporator, stockholder, limited partner, member, manager, employee, agent, officer, director or subsidiary, as such, past, present or future, of the Guarantor, the Issuer or any of the Issuer’s Subsidiaries or of any successor thereto, either directly or through the Guarantor, the Issuer or any of the Issuer’s subsidiaries or of any successor thereto, whether by virtue of any constitution, statute or rule of law, or by the enforcement of any assessment or penalty or otherwise; it being expressly understood that all such liability is hereby expressly waived and released as a condition of, and as consideration for, the execution of the Indenture and the issue of this Note.

ASSIGNMENT FORM

To assign this Note, fill in the form below:

(Insert assignee’s soc. sec. or tax I.D. no.)

(Print or type assignee’s name, address and zip code)

and irrevocably appoint                                to transfer this Note on the books of the Issuer.  The agent may substitute another to act for him.

* Participant in a recognized Signature Guarantee Medallion Program (or other signature guarantor acceptable to the Trustee).

SCHEDULE OF EXCHANGES OF INTERESTS IN THE GLOBAL NOTE *

The following exchanges of a part of this Global Note for an interest in another Global Note or for a Definitive Note, or exchanges of a part of another Global Note or Definitive Note for an interest in this Global Note, have been made:

*  This schedule should be included only if the Note is issued in global form.