| 1 | M & R Exploration Company | Houston, TX 77074 | Oil & Gas Operator | Aug 2003 |
| 2 | M & S Exploration | El Campo, TX 77437 | Oil & Gas Operator | Dec 2025 |
| 3 | M. J. G., Inc. | Alice, TX 78333 | Oil & Gas Operator | Jul 2010 |
| 4 | Maggert Energy Corp. | Spring, TX 77387 | Gas Operator | Jun 1998 |
| 5 | Magnum Engineering Company | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Dec 2025 |
| 6 | Magnum Producing & Operating Co. | Corpus Chrsti, TX 78471 | Oil & Gas Operator | Jan 2004 |
| 7 | Magnum Producing, LP | Corpus Chrsti, TX 78401 | Oil & Gas Operator | Dec 2025 |
| 8 | Mark IV Energy | San Antonio, TX 78213 | Oil & Gas Operator | Apr 1993 |
| 9 | Marquee Corporation | Houston, TX 77024 | Oil & Gas Operator | Dec 2025 |
| 10 | Marwell Petroleum LTD Partnrship | Houston, TX 77027 | Oil & Gas Operator | Dec 2025 |
| 11 | Marwell Petroleum, Inc. | Houston, TX 77057 | Oil & Gas Operator | Apr 2006 |
| 12 | Maverick Prod. Co., Inc. | Houston, TX 77056 | Oil & Gas Operator | Dec 2025 |
| 13 | Maxus Exploration Company | Dallas, TX 75201 | Oil & Gas Operator | Jan 1995 |
| 14 | Maynard Oil Co. | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 15 | Mayne & Mertz, Inc. | Midland, TX 79702 | Oil & Gas Operator | Mar 2013 |
| 16 | MB Energy, LLC | San Antonio, TX 78233 | Oil & Gas Operator | Dec 2025 |
| 17 | McBee Company, The | Dallas, TX 75219 | Oil & Gas Operator | Dec 1997 |
| 18 | McCarter, A. Nelson | Houston, TX 77063 | Oil & Gas Operator | Aug 2003 |
| 19 | McCauley, F. R. | Houston, TX 77002 | Oil & Gas Operator | Apr 2000 |
| 20 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 21 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Dec 2025 |
| 22 | McLeod, George L. Inc. | Houston, TX 77079 | Oil & Gas Operator | Sep 2002 |
| 23 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 24 | Medallion Oil Company | Houston, TX 77251 | Oil & Gas Operator | Jan 2012 |
| 25 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 26 | Meridian Oil Production Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 2024 |
| 27 | Metano Energy, LP | San Antonio, TX 78216 | Oil & Gas Operator | Aug 2008 |
| 28 | Mexco Energy Corporation | Midland, TX 79702 | Oil & Gas Operator | Feb 2020 |
| 29 | Midas Resources, Inc. | Corpus Chrsti, TX 78403 | Oil & Gas Operator | Dec 2025 |
| 30 | Midpar L.P. | Midland, TX 79702 | Oil & Gas Operator | Feb 1995 |
| 31 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 32 | Millennium Exploration Co. LLC | San Antonio, TX 78232 | Oil & Gas Operator | Dec 2025 |
| 33 | Miller, W. C. Operating Company | San Antonio, TX 78209 | Oil & Gas Operator | Dec 2025 |
| 34 | Miramar Petroleum, Inc. | Corpus Chrsti, TX 78463 | Oil & Gas Operator | Sep 2017 |
| 35 | Mission Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 36 | Mobil Producing TX. & N.M. Inc. | Spring, TX 77389 | Oil & Gas Operator | Dec 2025 |
| 37 | Mohican Oil & Gas, L.L.C. | Corpus Chrsti, TX 78476 | Oil & Gas Operator | Apr 2013 |
| 38 | Mojac Energy Corp. | Houston, TX 77056 | Oil & Gas Operator | Dec 1997 |
| 39 | Moose Oil & Gas Co. | Houston, TX 77002 | Oil & Gas Operator | Feb 2000 |
| 40 | Mosaic Oil LLC | Dallas, TX 75205 | Oil & Gas Operator | Dec 2025 |
| 41 | Mueller Engineering Corp. | Corpus Chrsti, TX 78476 | Oil & Gas Operator | Feb 2002 |
| 42 | Mueller Exploration, Inc. | Portland, TX 78374 | Oil & Gas Operator | Dec 2025 |
| 43 | Mustang Energy Inc. | Porter, TX 77365 | Oil & Gas Operator | Mar 2008 |
| 44 | Mustang Fuel Corporation | Oklahoma City, OK 73114 | Oil & Gas Operator | Sep 2025 |