| No. | Name | Type | Language | Counties |
|---|---|---|---|---|
| 2 | Jill Marie O'Donnell | Master | English | Douglas, Jackson, Josephine, Klamath, Lake |
| 1 | ERIN JEAN O'REGAN | Master | English | Multnomah |
| 2 | Amie O'Rourke | Master | English | Benton, Linn |
| 0 | EZELMA ANN OBUHORO | Master | English | Multnomah, Washington |
| 11 | RUTH NOEMI OCHOA | Master | English, Spanish | All |
| 0 | WHITNEY OCONNELL | Community | English | All |
| 23 | Soobin David Oh | Master | English | All |
| 118 | HEATHER OLEARY | Master | English | All |
| 1 | Katherine Elaine Olinger | Master | English | All |
| 0 | Yamel Olivas Solis | Standardized | Spanish | Clackamas, Multnomah, Washington, Yamhill |
| 0 | Laura Ann Olson | Master | English | Clackamas, Marion, Multnomah, Polk, Yamhill |
| 25 | Kim (Kiki) Omoto | Master | English | Benton |
| 2 | CHRISTINA SUZANNE ONEILL | Master | English | All |
| 3 | LISSET ONEILL | Master | English, Spanish | Multnomah |
| 1 | Nancy L Orem | Master | English | All |
| 1 | RAUL DAVID OROZCO FUENTES | Master | English, Spanish | Benton, Linn, Marion, Polk |
| 0 | Kay Guadalupe Ortega | Standardized | English, Spanish | Jackson, Jefferson, Josephine, Klamath |
| 0 | ELENA ESMERALDA ORTIZ-ROBLES | Community | Spanish | Hood River, Multnomah, Wasco |
| 0 | CINDY RAE OVERSTREET | Master | English | Clackamas, Clatsop, Columbia, Multnomah, Washington |
| 0 | KARISSA LYNN PALMER | Master | English | All |