| Name | Type | Language | Counties |
|---|---|---|---|
| Lisa Ann O'Connor | Master | English | Gilliam, Hood River, Sherman, Wasco, Wheeler |
| Jill Marie O'Donnell | Master | English | Douglas, Jackson, Josephine, Klamath, Lake |
| ERIN JEAN O'REGAN | Master | English | Multnomah |
| Amie O'Rourke | Master | English | Benton, Linn |
| HENRY OBELNICKI | Master | English | Clatsop, Columbia, Hood River, Lincoln, Multnomah, Washington |
| EZELMA ANN OBUHORO | Master | English | Multnomah, Washington |
| RUTH (Noemí) NOEMI OCHOA | Master | English, Spanish | All |
| WHITNEY OCONNELL | Community | English | All |
| Soobin David Oh | Master | English | All |
| HEATHER OLEARY | Master | English | All |
| Katherine Elaine Olinger | Master | English | All |
| Yamel Olivas Solis | Standardized | Spanish | Clackamas, Multnomah, Washington, Yamhill |
| ELIZABETH ANN OLSON | Standardized | ||
| Laura Ann Olson | Master | English | Clackamas, Marion, Multnomah, Polk, Yamhill |
| Kim (Kiki) Omoto | Master | English | Benton |
| CHRISTINA SUZANNE ONEILL | Master | English | All |
| LISSET ONEILL | Master | English, Spanish | Multnomah |
| Nancy L Orem | Master | English | All |
| RAUL DAVID OROZCO FUENTES | Master | English, Spanish | Benton, Linn, Marion, Polk |
| Kay Guadalupe Ortega | Standardized | English, Spanish | Jackson, Jefferson, Josephine, Klamath |