| Registered Name | Owner / Club | Status |
|---|---|---|
| Ogue Niamh | Kate Keenan Meath | Approved |
| Oh Be The Hokey (IRE) | Beverley Morgan Greenvalley | Approved |
| Oh Boss | Laurene Yviquel Cheval | Approved |
| Oh My Daisy | Kerry O'Sullivan Sarsfield | Approved |
| Oh Tea Tea | Bridget Hearne Barrow Valley | Approved |
| Oilean Aghercon | Lisa Lomax Benbulben | Approved |
| Oilean Hitachi | Finola Craven Highland Lodge | Approved |
| Oisin Blackthorn | Miriam McDonnell Lismore | Approved |
| Ojaspers Touch | Trina Maguire Lakelands | Approved |
| Ok Miss Rosie | Fidelma Clare Carne | Approved |
| Oka Della Corona (IRE) | Paul Kane Lakelands | Approved |
| Oke Lady | Aisling Donoghue Corrib | Approved |
| Oklahoma | Aidan Connelly South Roscommon | Approved |
| Oktober | Eamon McGuirk Gap of the North | Approved |
| Ol Harry Potter | Sarah Lee West Cork | Approved |