| 301 | Maynard Oil Co. | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 302 | McDaniel Company, Inc., The | Dallas, TX 75230 | Oil & Gas Operator | Jun 2026 |
| 303 | McGuffin, Joe Jr. | Christoval, TX 76935 | Oil & Gas Operator | Jun 2026 |
| 304 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 305 | Merrico Resources, Inc. | Ardmore, OK 73402 | Oil & Gas Operator | Mar 2008 |
| 306 | Mexco Energy Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2020 |
| 307 | MGM Well Service, Inc. | Corpus Chrsti, TX 78427 | Oil & Gas Operator | Oct 2004 |
| 308 | Mid-Continent Energy Operating Company | Tulsa, OK 74103 | Oil & Gas Operator | Mar 2026 |
| 309 | Mid-Continent Energy, Inc. | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2020 |
| 310 | Midcon Offshore, Inc. | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 311 | Midland Res. Oper. Co., Inc. | Midland, TX 79701 | Oil & Gas Operator | Oct 1998 |
| 312 | Midpar L.P. | Midland, TX 79702 | Oil & Gas Operator | Feb 1995 |
| 313 | Miller, W. C. Operating Company | San Antonio, TX 78209 | Oil & Gas Operator | Jun 2026 |
| 314 | Miltex Oil Company | Boerne, TX 78006 | Oil & Gas Operator | Jun 2026 |
| 315 | Mission River Systems, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Jun 2026 |
| 316 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 317 | Mobil Oil Corporation | Houston, TX 77210 | Oil & Gas Operator | Dec 2007 |
| 318 | Mobil Producing TX. & N.M. Inc. | Spring, TX 77389 | Oil & Gas Operator | Feb 2026 |
| 319 | Modern Exploration, Inc. | Sherman, TX 75090 | Oil & Gas Operator | Jun 2026 |
| 320 | Mohican Operating, L.L.C. | Corpus Christ, TX 78401 | Oil & Gas Operator | Apr 2021 |
| 321 | Monterey Resources LLC | Dallas, TX 75230 | Oil & Gas Operator | Oct 2019 |
| 322 | Morgan Enterprises, Inc. | Houston, TX 77024 | Oil & Gas Operator | Jun 2026 |
| 323 | Mowata Oil Company | Victoria, TX 77903 | Oil & Gas Operator | Oct 1996 |
| 324 | Mueller Engineering Corp. | Corpus Chrsti, TX 78476 | Oil & Gas Operator | Feb 2002 |
| 325 | Mueller Exploration, Inc. | Portland, TX 78374 | Oil & Gas Operator | Jun 2026 |
| 326 | Musselman, Owen & King Oper.,Inc | Houston, TX 77002 | Oil & Gas Operator | Feb 1998 |
| 327 | Mustang Oil & Gas Corporation | Wichita Falls, TX 76308 | Oil & Gas Operator | Jul 2021 |
| 328 | National Energy Group Inc | Dallas, TX 75206 | Oil & Gas Operator | Sep 2014 |
| 329 | Natural Gas Pipeline Co Of Amer. | Houston, TX 77002 | Gas Operator | Jul 2008 |
| 330 | NBL Permian LLC | Houston, TX 77070 | Oil & Gas Operator | Aug 2018 |
| 331 | Neg Operating LLC | Oklahoma City, OK 73101 | Oil & Gas Operator | Aug 2025 |
| 332 | Newman Operating Company | Freer, TX 78357 | Oil & Gas Operator | Jun 2021 |
| 333 | Noble Energy Inc | Midland, TX 79706 | Oil & Gas Operator | Jun 2026 |
| 334 | Norcen Explorer, Inc. | Houston, TX 77079 | Oil & Gas Operator | May 1998 |
| 335 | North Central Oil Corp | Houston, TX 77252 | Oil & Gas Operator | Dec 2005 |
| 336 | Northwest Oil Company | Dallas, TX 75204 | Oil & Gas Operator | Jun 2014 |
| 337 | Nueces Reserves, Inc. | Houston, TX 77019 | Oil & Gas Operator | Oct 2002 |
| 338 | Null, W.M. Operations, Inc. | Corpus Chrsti, TX 78475 | Oil & Gas Operator | Jun 2002 |
| 339 | Odegard Energy, Inc. | Houston, TX 77024 | Oil & Gas Operator | Jul 2020 |
| 340 | Oil Coast Corp. | S Houston, TX 77587 | Oil & Gas Operator | Jun 2026 |
| 341 | Oil Management Corporation | Dallas, TX 75206 | Oil & Gas Operator | Apr 2022 |
| 342 | Oldfield Acquisition LP | Austin, TX 78733 | Oil & Gas Operator | Sep 1996 |
| 343 | Oleum Operating Company, L.C. | Longview, TX 75606 | Oil & Gas Operator | Dec 2021 |
| 344 | Omega Energy Corp. | Graham, TX 76450 | Oil & Gas Operator | Jun 2026 |
| 345 | Omega Energy, LLC | Corpus Christ, TX 78418 | Oil & Gas Operator | Jun 2026 |
| 346 | Opex Energy, LLC | Houston, TX 77042 | Oil & Gas Operator | Mar 2008 |
| 347 | Orx Resources, L.L.C. | Houston, TX 77067 | Oil & Gas Operator | Jun 2026 |
| 348 | Oryx Energy Company | Dallas, TX 75221 | Oil & Gas Operator | May 2002 |
| 349 | Outline Oil Corp. | San Antonio, TX 78217 | Oil & Gas Operator | Jun 2026 |
| 350 | Overly Operating Co. | San Antonio, TX 78209 | Oil & Gas Operator | Jul 2013 |
| 351 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Jun 2026 |
| 352 | P-R-O Management, Inc. | Dallas, TX 75240 | Oil & Gas Operator | Jun 2026 |
| 353 | Palace Operating Company | Tulsa, OK 74136 | Oil & Gas Operator | Aug 2009 |
| 354 | Paleo Oil Company LLC | Corpus Christ, TX 78411 | Oil & Gas Operator | Jun 2026 |
| 355 | Paloma Operating, LLC | Corpus Christ, TX 78401 | Oil & Gas Operator | Jun 2026 |
| 356 | Pangea'S Edge Operating Company LLC | Plano, TX 75025 | Oil & Gas Operator | Jun 2026 |
| 357 | Panhandle Producing Company | San Antonio, TX 78205 | Oil & Gas Operator | Oct 1993 |
| 358 | Pantera Energy Company | Amarillo, TX 79101 | Oil & Gas Operator | Jun 2026 |
| 359 | Parker & Parsley Development L.P | Midland, TX 79702 | Oil & Gas Operator | Oct 2007 |
| 360 | Parker & Parsley Producing LP | Midland, TX 79702 | Oil & Gas Operator | Oct 1997 |
| 361 | Patton Oil Corp. | Corpus Chrsti, TX 78466 | Oil & Gas Operator | Aug 2003 |
| 362 | Payne, B.R. Oil & Gas, Inc. | Corpus Christ, TX 78411 | Oil & Gas Operator | Feb 2006 |
| 363 | Pearl, Bill H. Productions, Inc. | Corpus Chrsti, TX 78460 | Oil & Gas Operator | Jun 2026 |
| 364 | Pegasus Petroleum Corporation | Corpus Chrsti, TX 78476 | Oil & Gas Operator | Jun 2026 |
| 365 | Penn VIrginia Oil & Gas Corp | Houston, TX 77024 | Oil & Gas Operator | Dec 2023 |
| 366 | Penn VIrginia Oil & Gas, L.P. | Houston, TX 77084 | Oil & Gas Operator | Nov 2022 |
| 367 | Pennzenergy Exp. & Prod., L.L.C. | Houston, TX 77210 | Oil & Gas Operator | Mar 2000 |
| 368 | Pennzoil Exploration & Production Co. | Carthage, TX 75633 | Oil & Gas Operator | Mar 2008 |
| 369 | Peoples Energy Prod.-TX, L.P. | Houston, TX 77002 | Oil & Gas Operator | Sep 2007 |
| 370 | Permian Natural Resources | Tyler, TX 75701 | Oil & Gas Operator | Jun 2026 |
| 371 | Petro Resources, Inc. | Fulton, TX 78358 | Oil & Gas Operator | Jun 2026 |
| 372 | Petro-Guard Company, Inc. | Houston, TX 77057 | Oil & Gas Operator | Nov 2014 |
| 373 | Petro-Hunt Corporation | Dallas, TX 75201 | Oil & Gas Operator | Jun 2003 |
| 374 | Petro-Hunt, L.L.C. | Dallas, TX 75201 | Oil & Gas Operator | Jun 2026 |
| 375 | Petro-Smith Operating LLC | Houston, TX 77010 | Oil & Gas Operator | Jun 2026 |
| 376 | Petrodome Operating, LLC | Houston, TX 77265 | Oil & Gas Operator | May 2025 |
| 377 | Petrogulf Corporation | Denver, CO 80202 | Oil & Gas Operator | Jun 2026 |
| 378 | Petrohawk Operating Company | Houston, TX 77056 | Oil & Gas Operator | Oct 2021 |
| 379 | Petroleum Management, Inc. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Jun 2026 |
| 380 | Petroquest Exploration, Inc. | Dallas, TX 75251 | Oil & Gas Operator | Mar 2008 |
| 381 | Petrotex Engineering Company | Cypress, TX 77429 | Oil & Gas Operator | Jun 2026 |
| 382 | Phillips Petroleum Company | Houston, TX 77251 | Oil & Gas Operator | Mar 2013 |
| 383 | Pi Energy, Inc. | Wichita Falls, TX 76301 | Oil & Gas Operator | Jun 2026 |
| 384 | Pine Island Operating, L.L.C. | Graham, TX 76450 | Oil & Gas Operator | Jun 2026 |
| 385 | Pintail Oil & Gas, LLC | Midland, TX 79702 | Oil & Gas Operator | Dec 2019 |
| 386 | Pintex Operating Inc. | Corpus Chrsti, TX 78478 | Oil & Gas Operator | Feb 2005 |
| 387 | Pioneer Exploration Company | Houston, TX 77090 | Oil & Gas Operator | Mar 2026 |
| 388 | Pioneer Natural Res. USA, Inc. | Spring, TX 77389 | Oil & Gas Operator | Jun 2026 |
| 389 | Pioneer Resources Producing, L.P | Irving, TX 75039 | Oil & Gas Operator | Feb 2001 |
| 390 | Pittencrieff (Gulf Coast), Inc. | Abilene, TX 79608 | Oil & Gas Operator | Sep 1998 |
| 391 | Pittencrieff America Inc | Abilene, TX 79608 | Oil & Gas Operator | Feb 2003 |
| 392 | Placer Oil Co. | Sugar Land, TX 77479 | Oil & Gas Operator | Apr 2008 |
| 393 | Plains Resources Inc. | Houston, TX 77002 | Oil & Gas Operator | Jul 2008 |
| 394 | Powerline Energy Corporation | Arlington, TX 76015 | Oil & Gas Operator | Jun 2026 |
| 395 | Preferred Pipeline Corp. | Victoria, TX 77902 | Oil & Gas Operator | Apr 2026 |
| 396 | Premier Minerals, Inc. | San Antonio, TX 78209 | Oil & Gas Operator | Jun 2026 |
| 397 | Prevail Energy, Inc | Corpus Christ, TX 78469 | Oil & Gas Operator | Jun 2026 |
| 398 | Pride Energy Company | Tulsa, OK 74170 | Oil & Gas Operator | Jun 2026 |
| 399 | Princess Three Corporation | Henderson, TX 75653 | Oil & Gas Operator | Apr 2020 |
| 400 | Prize Operating Company | Grapevine, TX 76051 | Oil & Gas Operator | Aug 2016 |