1 EXHIBIT 99.1 [MESA LOGO] Dear Stockholder: You are cordially invited to attend the Special Meeting of Stockholders of MESA Inc. on August 7, 1997. At this meeting, stockholders will be asked to approve certain matters relating to the proposed merger with Parker & Parsley Petroleum Company announced April 6, 1997. The meeting will begin at 2:00 p.m. at the Wyndham Anatole Hotel, Wedgwood Room, 2201 Stemmons Freeway, Dallas, Texas. For your convenience, we are including a map on the reverse side of this letter that will be useful in planning your activities should you decide to attend the meeting. After reviewing the enclosed material, please take a moment to sign, date and mark your vote on the proxy card below and return it in the enclosed postage-paid envelope. While management is recommending a vote "FOR" each of the issues outlined below and would appreciate your support, we urge your careful review of the enclosed material so that you can make your own determination on how to vote. We believe all stockholders should have a voice in the Company's direction, so we ask that you return the proxy card whether or not you plan to attend the special meeting. If you have any questions or require additional information with respect to the proposed merger, please contact MESA's information agent, Morrow & Co. Inc. at 1-800-566-9058. I look forward to seeing you on August 7th. Jon Brumley Chairman of the Board and Chief Executive Officer FOLD AND TEAR HERE FOLD AND TEAR HERE FOLD AND TEAR HERE - -------------------------------------------------------------------------------- PROXY PROXY MESA INC. PROXY SOLICITED BY THE BOARD OF DIRECTORS FOR THE SPECIAL MEETING OF STOCKHOLDERS TO BE HELD AUGUST 7, 1997 The undersigned stockholder hereby appoints M. Garrett Smith and G. Michael Prescott, jointly and severally, as proxies, with full power of substitution, to vote, as specified below, all shares of Common Stock, par value $0.01 per share ("Common Stock"), of MESA Inc. (the "Company") that the undersigned is entitled to vote at the Special Meeting of Stockholders of the Company to be held at the Wyndham Anatole Hotel, Wedgwood Room, 2201 Stemmons Freeway, Dallas, Texas, at 2:00 p.m. on August 7, 1997, or any adjournment or postponement thereof (the "Special Meeting"), and directs said proxies to vote as instructed on the matters set forth below AND OTHERWISE AT THEIR DISCRETION. Receipt of a copy of the Notice of said Special Meeting and the accompanying Joint Proxy Statement/Prospectus is hereby acknowledged. This proxy revokes all prior proxies given by the undersigned with respect to the Common Stock. Please sign EXACTLY as name(s) appears hereon, and in signing as Attorney, Administrator, Guardian, Trustee or Corporate Officer, please add your title as such. Signature_____________________________ Title_________________________________ Date_______________________________1997 USE THIS CARD ONLY TO VOTE SHARES OF MESA INC. COMMON STOCK 2 MEETING LOCATION [REVERSE SIDE] DALLAS, TEXAS [Map] The Special Meeting will be held in the Wedgwood Room of the Wyndham Anatole Hotel, 2201 Stemmons Freeway, Dallas, Texas. Parking is conveniently located at the entrances in front of the hotel. - -------------------------------------------------------------------------------- THE BOARD OF DIRECTORS RECOMMENDS A VOTE FOR PROPOSAL 1, PROPOSAL 2, PROPOSAL 3 AND PROPOSAL 4 SET FORTH BELOW. Proposal 1. Approve and adopt the Agreement and Plan of Merger among the Company, Mesa Operating Co., Pioneer Natural Resources Company and Parker & Parsley Petroleum Company. [ ] FOR [ ] AGAINST [ ] ABSTAIN Proposal 2. Approve the adoption of the Mesa 1996 Incentive Plan. [ ] FOR [ ] AGAINST [ ] ABSTAIN Proposal 3. Approve the adoption of the Pioneer Long-Term Incentive Plan. [ ] FOR [ ] AGAINST [ ] ABSTAIN Proposal 4. Approve the adoption of the Pioneer Employee Stock Purchase Plan. [ ] FOR [ ] AGAINST [ ] ABSTAIN PROPOSAL ONE IS NOT CONDITIONED ON THE APPROVAL OF ANY OF THE OTHER PROPOSALS. PROPOSAL TWO IS NOT CONDITIONED ON THE APPROVAL OF ANY OF THE OTHER PROPOSALS. NEITHER PROPOSAL THREE NOR PROPOSAL FOUR WILL BE IMPLEMENTED UNLESS PROPOSAL ONE IS APPROVED. THIS PROXY, WHEN PROPERLY EXECUTED, WILL BE VOTED IN THE MANNER DIRECTED HEREIN. WHERE NO VOTE IS SPECIFIED FOR A PROPOSAL, THIS PROXY WILL BE VOTED "FOR" SUCH PROPOSAL. THE INDIVIDUALS NAMED HEREIN ARE AUTHORIZED TO VOTE IN THEIR DISCRETION ON ANY OTHER MATTERS THAT PROPERLY COME BEFORE THE SPECIAL MEETING. USE THIS CARD ONLY TO VOTE SHARES OF MESA INC. COMMON STOCK 3 4 [MESA LOGO] Dear Stockholder: You are cordially invited to attend the Special Meeting of Stockholders of MESA Inc. on August 7, 1997. At this meeting, stockholders will be asked to approve certain matters relating to the proposed merger with Parker & Parsley Petroleum Company announced April 6, 1997. The meeting will begin at 2:00 p.m. at the Wyndham Anatole Hotel, Wedgwood Room, 2201 Stemmons Freeway, Dallas, Texas. For your convenience, we are including a map on the reverse side of this letter that will be useful in planning your activities should you decide to attend the meeting. After reviewing the enclosed material, please take a moment to sign, date and mark your vote on the proxy card below and return it in the enclosed postage-paid envelope. While management is recommending a vote "FOR" each of the issues outlined below and would appreciate your support, we urge your careful review of the enclosed material so that you can make your own determination on how to vote. We believe all stockholders should have a voice in the Company's direction, so we ask that you return the proxy card whether or not you plan to attend the special meeting. If you have any questions or require additional information with respect to the proposed merger, please contact MESA's information agent, Morrow & Co. Inc. at 1-800-566-9058. I look forward to seeing you on August 7th. Jon Brumley Chairman of the Board and Chief Executive Officer FOLD AND TEAR HERE FOLD AND TEAR HERE FOLD AND TEAR HERE - -------------------------------------------------------------------------------- PROXY PROXY MESA INC. PROXY SOLICITED BY THE BOARD OF DIRECTORS FOR THE SPECIAL MEETING OF STOCKHOLDERS TO BE HELD AUGUST 7, 1997 The undersigned stockholder hereby appoints M. Garrett Smith and G. Michael Prescott, jointly and severally, as proxies, with full power of substitution, to vote, as specified below, all shares of Series A 8% Cumulative Convertible Preferred Stock, par value $0.01 per share ("Series A Preferred Stock"), of MESA Inc. (the "Company") that the undersigned is entitled to vote at the Special Meeting of Stockholders of the Company to be held at the Wyndham Anatole Hotel, Wedgwood Room, 2201 Stemmons Freeway, Dallas, Texas, at 2:00 p.m. on August 7, 1997, or any adjournment or postponement thereof (the "Special Meeting"), and directs said proxies to vote as instructed on the matters set forth below AND OTHERWISE AT THEIR DISCRETION. Receipt of a copy of the Notice of said Special Meeting and the accompanying Joint Proxy Statement/Prospectus is hereby acknowledged. This proxy revokes all prior proxies given by the undersigned with respect to the Series A Preferred Stock. Please sign EXACTLY as name(s) appears hereon, and in signing as Attorney, Administrator, Guardian, Trustee or Corporate Officer, please add your title as such. Signature ------------------------------------ Title ---------------------------------------- Date 1997 ----------------------------- USE THIS CARD ONLY TO VOTE SHARES OF MESA INC. SERIES A PREFERRED STOCK 5 MEETING LOCATION [REVERSE SIDE] DALLAS, TEXAS [Map] The Special Meeting will be held in the Wedgwood Room of the Wyndham Anatole Hotel, 2201 Stemmons Freeway, Dallas, Texas. Parking is conveniently located at the entrances in front of the hotel. - -------------------------------------------------------------------------------- THE BOARD OF DIRECTORS RECOMMENDS A VOTE FOR PROPOSAL 1, PROPOSAL 2, PROPOSAL 3 AND PROPOSAL 4 SET FORTH BELOW. Proposal 1. Approve and adopt the Agreement and Plan of Merger among the Company, Mesa Operating Co., Pioneer Natural Resources Company and Parker & Parsley Petroleum Company. [ ] FOR [ ] AGAINST [ ] ABSTAIN Proposal 2. Approve the adoption of the Mesa 1996 Incentive Plan. [ ] FOR [ ] AGAINST [ ] ABSTAIN Proposal 3. Approve the adoption of the Pioneer Long-Term Incentive Plan. [ ] FOR [ ] AGAINST [ ] ABSTAIN Proposal 4. Approve the adoption of the Pioneer Employee Stock Purchase Plan. [ ] FOR [ ] AGAINST [ ] ABSTAIN PROPOSAL ONE IS NOT CONDITIONED ON THE APPROVAL OF ANY OF THE OTHER PROPOSALS. PROPOSAL TWO IS NOT CONDITIONED ON THE APPROVAL OF ANY OF THE OTHER PROPOSALS. NEITHER PROPOSAL THREE NOR PROPOSAL FOUR WILL BE IMPLEMENTED UNLESS PROPOSAL ONE IS APPROVED. THIS PROXY, WHEN PROPERLY EXECUTED, WILL BE VOTED IN THE MANNER DIRECTED HEREIN. WHERE NO VOTE IS SPECIFIED FOR A PROPOSAL, THIS PROXY WILL BE VOTED "FOR" SUCH PROPOSAL. THE INDIVIDUALS NAMED HEREIN ARE AUTHORIZED TO VOTE IN THEIR DISCRETION ON ANY OTHER MATTERS THAT PROPERLY COME BEFORE THE SPECIAL MEETING. USE THIS CARD ONLY TO VOTE SHARES OF MESA INC. SERIES A PREFERRED STOCK 6 [MESA LOGO] Dear Stockholder: You are cordially invited to attend the Special Meeting of Stockholders of MESA Inc. on August 7, 1997. At this meeting, stockholders will be asked to approve certain matters relating to the proposed merger with Parker & Parsley Petroleum Company announced April 6, 1997. The meeting will begin at 2:00 p.m. at the Wyndham Anatole Hotel, Wedgwood Room, 2201 Stemmons Freeway, Dallas, Texas. For your convenience, we are including a map on the reverse side of this letter that will be useful in planning your activities should you decide to attend the meeting. After reviewing the enclosed material, please take a moment to sign, date and mark your vote on the proxy card below and return it in the enclosed postage-paid envelope. While management is recommending a vote "FOR" each of the issues outlined below and would appreciate your support, we urge your careful review of the enclosed material so that you can make your own determination on how to vote. We believe all stockholders should have a voice in the Company's direction, so we ask that you return the proxy card whether or not you plan to attend the special meeting. If you have any questions or require additional information with respect to the proposed merger, please contact MESA's information agent, Morrow & Co. Inc. at 1-800-566-9058. I look forward to seeing you on August 7th. Jon Brumley Chairman of the Board and Chief Executive Officer FOLD AND TEAR HERE FOLD AND TEAR HERE FOLD AND TEAR HERE - -------------------------------------------------------------------------------- PROXY PROXY MESA INC. PROXY SOLICITED BY THE BOARD OF DIRECTORS FOR THE SPECIAL MEETING OF STOCKHOLDERS TO BE HELD AUGUST 7, 1997 The undersigned stockholder hereby appoints M. Garrett Smith and G. Michael Prescott, jointly and severally, as proxies, with full power of substitution, to vote, as specified below, all shares of Series B 8% Cumulative Convertible Preferred Stock, par value $0.01 per share ("Series B Preferred Stock"), of MESA Inc. (the "Company") that the undersigned is entitled to vote at the Special Meeting of Stockholders of the Company to be held at the Wyndham Anatole Hotel, Wedgwood Room, 2201 Stemmons Freeway, Dallas, Texas, at 2:00 p.m. on August 7, 1997, or any adjournment or postponement thereof (the "Special Meeting"), and directs said proxies to vote as instructed on the matters set forth below AND OTHERWISE AT THEIR DISCRETION. Receipt of a copy of the Notice of said Special Meeting and the accompanying Joint Proxy Statement/Prospectus is hereby acknowledged. This proxy revokes all prior proxies given by the undersigned with respect to the Series B Preferred Stock. Please sign EXACTLY as name(s) appears hereon, and in signing as Attorney, Administrator, Guardian, Trustee or Corporate Officer, please add your title as such. Signature ------------------------------------ Title ---------------------------------------- Date 1997 ----------------------------- USE THIS CARD ONLY TO VOTE SHARES OF MESA INC. SERIES B PREFERRED STOCK