| # | Company name | Role | # of projects |
|---|---|---|---|
| 1 | O & S Associates | Architect | 0 |
| 2 | O Architects | Architect | 17 |
| 3 | O Dietz and Associates | Architect | 7 |
| 4 | O Escalante Architects | Architect | 0 |
| 5 | O Inc. | Architect | 1 |
| 6 | O Marvin Johnson Arch | Architect | 0 |
| 7 | O Robertson & Assoc | Architect | 3 |
| 8 | O T A Partnership | Architect | 1 |
| 9 | O Terasawa Partners | Architect | 0 |
| 10 | O Wicklund Pigozzi & Peterson Inc | Architect | 2 |
| 11 | O Wilson & Westphal | Architect | 1 |
| 12 | O. F. Sunde | Architect | 1 |
| 13 | O. Knebel | Architect | 0 |
| 14 | O. Roy Moore | Architect | 2 |
| 15 | O. Stefanutti | Architect | 1 |
| 16 | O. van Sprew | Architect | 1 |
| 17 | O.C. Uehling | Architect | 1 |
| 18 | O.E. Gonzalez | Architect | 1 |
| 19 | O.E. Guettler | Architect | 1 |
| 20 | O.K. Houstoun | Architect | 5 |