| 1 | O G & E | Oklahoma City, OK 73124-0300 | Oil & Gas Operator | Feb 2014 |
| 2 | O K Swabbing Inc | Hennessey, OK 73742-0835 | Oil & Gas Operator | Jan 2024 |
| 3 | Occidental Energy MKT Inc | Houston, TX 77001 | Oil & Gas Operator | Jan 2011 |
| 4 | Oil Recovery Systems Inc | | Oil & Gas Operator | Jan 2024 |
| 5 | Oilco Gas Co LC | Duncan, OK 73534 | Oil & Gas Operator | Dec 2014 |
| 6 | Okie Crude Company | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2024 |
| 7 | Oklahoma Liquid Resources Inc | Owasso, OK 74055-0841 | Oil & Gas Operator | Jan 2024 |
| 8 | Oklahoma Oil & Gas MGMT Inc | | Oil & Gas Operator | Jan 2024 |
| 9 | Oklahoma Oil And Gas Resources LLC | | Oil & Gas Operator | Jan 2024 |
| 10 | Oklahoma Petroleum Allies LLC | Ardmore, OK 73401 | Oil Operator | Oct 2023 |
| 11 | Oklahoma Tank Service Inc | Oklahoma City, OK 73143 | Oil Operator | Aug 1997 |
| 12 | Okland Oil Company | Oklahoma City, OK 73102-9022 | Oil & Gas Operator | Feb 2024 |
| 13 | Old Dominion Oil Corporation | Oklahoma City, OK 73107 | Oil & Gas Operator | Apr 2009 |
| 14 | Oneok Exploration Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 15 | Oneok Field Services Company | Tulsa, OK 74103 | Oil & Gas Operator | Jul 2022 |
| 16 | Oneok Resources Company | Tulsa, OK 74102 | Oil & Gas Operator | Feb 2017 |
| 17 | Oryx Crude Trading & Transporation LP | Dallas, TX 75221 | Oil & Gas Operator | Jun 1999 |
| 18 | Otc Petroleum Corporation | Oklahoma City, OK 73116 | Oil & Gas Operator | Mar 2015 |
| 19 | Ouachita Exploration Inc | Chickasha, OK 73023-0926 | Oil & Gas Operator | Jan 2024 |
| 20 | Ovintiv Mid-Continent Inc. | The Woodlands, TX 77380-2764 | Oil & Gas Operator | Jan 2024 |
| 21 | Oxley Petroleum | Tulsa, OK 74119-3609 | Oil & Gas Operator | Jan 2020 |
| 22 | Oxley Petroleum Co | Oklahoma City, OK 73118-1044 | Oil & Gas Operator | Sep 2017 |
| 23 | Oxy USA Inc | Houston, TX 77046 | Oil & Gas Operator | Apr 2024 |