| Breeders and Owners | DOWNLOAD Membership Application |
| A | | B | | C | | D | | E | | F | | G | | H | | I | | J | | K | | L | | M | | N | | O | | P | Q | | R | | S | | T | | U | | V | | W | | X | | Y | | Z |
| O |
| Oak Lane Stables | 1705 |
| O'Brien, Errol | 1336 |
| O'Brien, Mr & Mrs Pj & Jl | 1586 |
| O'Connor, Cara | 1679 |
| O'Connor, Morris | 1703 |
| O'Flaherty, Mr Brian | 1473 |
| Okiwa Stud | 1596 |
| Olaman, Aj & Cj | 1589 |
| O'Leary, Sonya | 1212 |
| Olive, Stephanie | 1756 |
| O'More, Mrs Wendy | 1106 |
| One Day | 1785 |
| Orchard, Mrs F.W. | 1502 |
| O'Regan, Phil B | 1174 |
| Orlando-Reep, Mrs Kim | 1370 |
| Ormond Quarter Horse Stud | 1528 |
| Orr, Walter | 1595 |
| Otto, Judith | 1754 |
| Outlaw Pintos (Suffix Ol) | 1753 |