| 1 | Oil Operations Inc | | Oil & Gas Operator | Apr 2011 |
| 2 | Okla Petroleum Energies Corp | | Oil Operator | Jan 2013 |
| 3 | Oklahoma Liquid Resources Inc | Owasso, OK 74055-0841 | Oil & Gas Operator | Jan 2024 |
| 4 | Oklahoma Petroleum Allies LLC | Ardmore, OK 73401 | Oil Operator | Oct 2023 |
| 5 | Orloski John C | Bartlesville, OK 74006-9040 | Oil & Gas Operator | Jan 2024 |
| 6 | Osage Energy Resources LLC | Bartlesville, OK 74005-2527 | Oil & Gas Operator | Jan 2024 |
| 7 | Oswego Arbuckle Enterprise Inc | S Coffeyville, OK 74072-9702 | Oil & Gas Operator | Mar 2015 |
| 8 | Ovintiv Mid-Continent Inc. | The Woodlands, TX 77380-2764 | Oil & Gas Operator | Jan 2024 |