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                                                                     EXHIBIT 4.1

                          AMENDMENT TO RIGHTS AGREEMENT

         Amendment dated as of February 25, 2004, to the Rights Agreement, dated
as of September 12, 1997 (the "Rights Agreement"), between Mission Resources
Corporation, a Delaware corporation formerly known as Bellwether Exploration
Company (the "Company"), and American Stock Transfer & Trust Company, a New York
corporation, as Rights Agent (the "Rights Agent"), as amended to date.

         WHEREAS, the Company and the Rights Agent entered into the Rights
Agreement specifying the terms of the Rights (as defined therein);

         WHEREAS, the Company desires to amend the Rights Agreement in
accordance with Section 27 of the Rights Agreement;

         WHEREAS, the Company proposes to enter into a Purchase and Sale
Agreement dated as of February 25, 2004 (the "Purchase Agreement"), by and
between Stellar Funding Ltd. ("Stellar") and the Company;

         WHEREAS, the Board of Directors of the Company has determined it
advisable and in the best interest of its stockholders to amend the Rights
Agreement to enable the Company to enter into the Purchase Agreement and
consummate the transactions contemplated thereby without causing Stellar or any
of their respective affiliates or associates to become an "Acquiring Person" (as
defined in the Rights Agreement).

         NOW, THEREFORE, in consideration of the premises and mutual agreements
set forth herein and in the Rights Agreement, the parties hereby agree as
follows:

         Section 1. Definitions. Capitalized terms used and not otherwise
defined herein shall have the meaning assigned to such terms in the Rights
Agreement.

         Section 2. Amendments to Rights Agreement. The Rights Agreement is
hereby amended as set forth in this Section 2.

         (a) The definition of "Acquiring Person" in Section 1 of the Rights
Agreement is amended to add the following sentence at the end thereof:

         "Notwithstanding anything in this Agreement to the contrary, neither of
         Stellar or any Affiliate or Associate of any of them shall be deemed to
         be an Acquiring Person, either individually or collectively, solely by
         virtue of (i) the execution and delivery of the Stellar Purchase
         Agreement, or (ii) the issuance and delivery of shares of Common Stock
         in accordance with Article 2 of the Stellar Purchase Agreement."

         (b) The definition of "Distribution Date" in Section 1 of the Rights
Agreement is amended to add the following sentence at the end thereof:

         "Notwithstanding anything in this Agreement to the contrary, a
         Distribution Date shall not be deemed to have occurred solely as the
         result of (i) the execution and


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         delivery of the Stellar Purchase Agreement, or (ii) the issuance and
         delivery of shares of Common Stock in accordance with Article 2 of the
         Stellar Purchase Agreement."

         (c) The definition of "Stock Acquisition Date" in Section 1 of the
Rights Agreement is amended to add the following sentence at the end thereof:

         "Notwithstanding anything in this Agreement to the contrary, a Stock
         Acquisition Date shall not be deemed to have occurred solely as the
         result of (i) the execution and delivery of the Stellar Purchase
         Agreement, or (ii) the issuance and delivery of shares of Common Stock
         in accordance with Article 2 of the Stellar Purchase Agreement."

         (e) The following definitions shall be added to Section 1 of the Rights
Agreement:

         "`Stellar' shall mean Stellar Funding Ltd."

          "`Stellar Purchase Agreement' shall mean the Purchase and Sale
         Agreement dated as of February 25, 2004, by and between Stellar and the
         Company."

         Section 3. Miscellaneous.

         (a) The term "Agreement" as used in the Rights Agreement shall be
deemed to refer to the Rights Agreement as amended to date and as amended
hereby.

         (b) This Amendment shall be effective as of the date first above
written, and, except as set forth herein, the Rights Agreement shall remain in
full force and effect and shall be otherwise unaffected hereby.

         (c) This Amendment may be executed in two or more counterparts, each of
which shall be deemed to be an original, but all for which together shall
constitute one and the same instrument.

         (d) This Amendment shall be deemed to be a contract made under the laws
of the State of Delaware and for all purposes shall be governed by and construed
in accordance with the laws of such State applicable to contracts to be made and
performed entirely within such State.

                            [SIGNATURE PAGE FOLLOWS]



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         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and attested, all as of the day and year first above written.


Attest:                                       MISSION RESOURCES CORPORATION


By: /s/ Ann Kaesermann                        By: /s/ Richard W. Piacenti
  ----------------------------------             -------------------------------
Name: Ann Kaesermann                          Name:    Richard W. Piacenti
     -------------------------------               -----------------------------
Title: VP Accounting & Investor Relations     Title: Executive VP and CFO
      -----------------------------------           ----------------------------


Attest:                                       AMERICAN STOCK TRANSFER &
                                                        TRUST COMPANY


By: /s/ Susan Silber                          By: /s/ Paula Caroppoli
  ----------------------------------             -------------------------------
Name: Susan Silber                            Name: Paula Caroppoli
      ------------------------------                ----------------------------
Title: Assistant Secretary                    Title: Vice President
      ------------------------------                ----------------------------





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