| 1 | Okie Operating Company, LTD. | Tulsa, OK 74103 | Oil & Gas Operator | Dec 2025 |
| 2 | Oklahoma Marlin Oil Corporation | Oklahoma City, OK 73113 | Oil & Gas Operator | Feb 2020 |
| 3 | Oklahoma RB Operating Company | Midland, TX 79701 | Oil & Gas Operator | Jan 1998 |
| 4 | Oklahoma Sterling Oil & Gas Corp | Tulsa, OK 74170 | Oil & Gas Operator | Jun 1997 |
| 5 | Oneok Exploration Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 6 | Opal Operating Company LLC | Edmond, OK 73013 | Oil & Gas Operator | Dec 2025 |
| 7 | Oringderff, Alma Oil Properties | Dallas, TX 75225 | Oil & Gas Operator | Mar 2012 |
| 8 | Orion Oil & Gas Properties | Amarillo, TX 79109 | Gas Operator | Oct 2000 |
| 9 | Otc Petroleum Corporation | Nichols Hill, OK 73116 | Oil & Gas Operator | Mar 2015 |
| 10 | Overflow Energy, LLC | Perryton, TX 79070 | Oil & Gas Operator | Dec 2025 |