BRANDYWINE OPERATING PARTNERSHIP, L.P. 7.50% Guaranteed Notes Due 2015

Exhibit 4.1

THIS NOTE IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE THEREOF. UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR NOTES IN CERTIFICATED FORM, THIS NOTE MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY.

UNLESS THIS NOTE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY (“DTC”) TO THE ISSUER OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY NOTE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS 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.

BRANDYWINE OPERATING PARTNERSHIP, L.P.

7.50% Guaranteed Notes Due 2015

          BRANDYWINE OPERATING PARTNERSHIP, L.P., a Delaware limited partnership (the “Issuer”, which term includes any successor entity under the Indenture hereinafter referred to), for value received, hereby promises to pay to Cede & Co., as the nominee of DTC, or registered assigns, the principal sum of TWO HUNDRED FIFTY MILLION DOLLARS ($250,000,000) on May 15, 2015, unless redeemed on any Redemption Date (as defined on the reverse hereof), and to pay interest on the outstanding principal amount of this Note from September 25, 2009 (or from the most recent Interest Payment Date (as defined below) to which interest has been paid or duly provided for), semiannually in arrears on May 15 and November 15 of each year, commencing on May 15, 2010 (the “Interest Payment Dates”), at the rate of 7.50% per annum, until payment of said principal amount has been paid or duly provided for. Interest on this Note will be computed on the basis of a 360-day year of twelve 30-day months.

          The interest so payable and punctually paid or duly provided for on any Interest Payment Date will be paid, as provided in the Indenture, to the Person in whose name this Note (or one or more Predecessor Securities) is registered at the close of business on the “Regular Record Date” for such payment, which will be the May 1 and November 1 (regardless of whether such day is a Business Day) immediately preceding such Interest Payment Date. Any

such interest not so punctually paid or duly provided for on an Interest Payment Date (“Defaulted Interest”) will forthwith cease to be payable to the Holder on such Regular Record Date, and may either be paid to the Person in whose name this Note (or one or more Predecessor Securities) is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, with notice whereof given by mail by or on behalf of the Issuer to the Holder of this Note not less than 10 days prior to such Special Record Date (which will be not more than 15 days and not less than 10 days prior to the date of the proposed payment of such Defaulted Interest), or may be paid at any time in any other lawful manner, all as more fully provided for in the Indenture (as defined on the reverse hereof).

          Payment of the principal of and Make-Whole Amount (as defined on the reverse hereof), if any, and interest on this Note will be made at the office or agency of the Issuer maintained by the Issuer for such purpose in the Borough of Manhattan, The City of New York, which initially will be the Corporate Trust Office of The Bank of New York Mellon, the Trustee for this Note under the Indenture, located at 101 Barclay Street, Floor 8W, Attention: Corporate Trust Administration, New York, New York 10286, in such coin or currency of the United States as at the time of payment is legal tender for payment of public and private debts; provided , however , that at the option of the Issuer payment of interest may be made by check mailed to the address of the Person entitled thereto as such address will appear in the Security Register or by wire transfer of funds to the Person entitled thereto at a bank account maintained in the United States.

          Reference is hereby made to the further provisions of this Note set forth on the reverse hereof, which such further provisions will for all purposes have the same effect as if set forth at this place.

          Unless the certificate of authentication hereon has been executed by or on behalf of The Bank of New York Mellon, the Trustee for this Note under the Indenture, or its successor thereunder, by the manual signature of one of its authorized officers, this Note will not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose.

          IN WITNESS WHEREOF, the Issuer has caused this instrument to be duly executed, manually or in facsimile, and an imprint or facsimile of its seal to be imprinted hereon.

Dated: September 25, 2009

CERTIFICATE OF AUTHENTICATION

          This is one of the Securities of the series designated therein described in the within-mentioned Indenture.

[REVERSE OF NOTE]

BRANDYWINE OPERATING PARTNERSHIP, L.P.

7.50% Guaranteed Notes Due 2015

          This Note is one of a duly authorized issue of securities of the Issuer (the “Securities”), issued or to be issued under and pursuant to an Indenture, dated as of October 22, 2004, as supplemented (the “Indenture”), among the Issuer, Brandywine Realty Trust, a Maryland real estate investment trust (the “Parent Guarantor”), and The Bank of New York Mellon, as Trustee (the “Trustee,” which term includes any successor Trustee under the Indenture with respect to the series of Securities of which this Note is a part), to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights thereunder of the Issuer, the Parent Guarantor, the Trustee and the Holders of the Securities and the terms upon which the Securities are to be authenticated and delivered. The Securities may be issued in one or more series, which different series may be issued in various aggregate principal amounts, may mature at different times, may bear interest (if any) at different rates, may be subject to different redemption provisions (if any), and may otherwise vary as provided in the Indenture. This Note is one of a series of Securities designated as the “7.50% Guaranteed Notes due 2015” of the Issuer (the “Notes”), initially limited in aggregate principal amount to $250,000,000 . The Issuer may, from time to time, without the consent of the Holders, issue and sell additional Securities ranking equally with the Notes and otherwise identical in all respects (except for their date of issuance, issue price and the date from which interest payments thereon will accrue) so that such additional Securities will be consolidated and form a single series with the Notes .

          The Notes are fully and unconditionally guaranteed as to the due and punctual payment of principal of and Make-Whole Amount, if any, and interest on the Notes by the Parent Guarantor.

          All terms used in this Note which are defined in the Indenture will have the meanings assigned to them in the Indenture.

          The Issuer may redeem this Note, at any time, in whole or in part, at its option, at a redemption price (the “Redemption Price”) equal to the greater of: (i) 100% of the principal amount of the Notes then outstanding to be redeemed, and (ii) the sum of the present values of the remaining scheduled payments of principal and interest on the Notes to be redeemed (not including any portion of such payments of interest accrued to the date of redemption) discounted to the date of redemption on a semiannual basis (assuming a 360-day year consisting of twelve 30-day months) at the applicable Treasury Rate plus 75 basis points (“Make-Whole Amount”), plus, in the case of either (i) or (ii) above, accrued and unpaid interest on the principal amount being redeemed to the date fixed for redemption (the “Redemption Date”).

          The following terms have the meanings specified below:

          “Treasury Rate” means, with respect to any Redemption Da