| City/Town | Area Code | Zip Code | County | Code |
| Oakhurst | 918 | 74050 | Tulsa | 40143 |
| Oakland | 405 | 73446 | Marshall | 40095 |
| Oaks | 918 | 74359 | Delaware | 40041 |
| Oakwood | 405 | 73658 | Dewey | 40043 |
| Ochelata | 918 | 74051 | Washington | 40147 |
| Octavia | 405 | 74957 | McCurtain | 40089 |
| Oilton | 918 | 74052 | Creek | 40037 |
| Okarche | 405 | 73762 | Canadian | 40017 |
| Kingfisher | 40073 | |||
| Okay | 918 | 74446 | Wagoner | 40145 |
| Okeene | 405 | 73763 | Blaine | 40011 |
| Okemah | 918 | 74859 | Okfuskee | 40107 |
| Okla. City | 405 | 73100 | Oklahoma | 40109 |
| thru | ||||
| 73189 | ||||
| Okmulgee | 918 | 74447 | Okmulgee | 40111 |
| Oktaha | 918 | 74450 | Muskogee | 40101 |
| Oleta | 405 | 74735 | Pushmataha | 40127 |
| Olustee | 405 | 73560 | Jackson | 40065 |
| Omega | 405 | 73764 | Kingfisher | 40073 |
| Oologah | 918 | 74053 | Rogers | 40131 |
| Optima | 405 | 73945 | Texas | 40139 |
| Orienta | 405 | 73737 | Major | 40093 |
| Orlando | 405 | 73073 | Logan | 40083 |
| Osage | 405 | 74604 | Kay | 40071 |
| Osage | 918 | 74054 | Osage | 40113 |
| Oscar | 405 | 73561 | Jefferson | 40067 |
| Overbrook | 405 | 73453 | Love | 40085 |
| Owasso | 918 | 74055 | Tulsa | 40143 |