| Open-fermented Barleywine | Zillicoah Beer Company | English Barleywine | 11.1% |
| Openfaced | To Øl | English Brown Ale | 9.0% |
| Opéra Framboise | brasseurs Simple Malt | | 11.4% |
| Opera Omnia | Brujos Brewing | American Imperial Stout | 12.9% |
| Operation CoHoperation | Lupulin Brewing/Barrel Theory | | 8.0% |
| Operation Cohoperation | Mumford Brewing | Imperial IPA | 8.0% |
| Operation Doomsday | Brouwerij Frontaal | New England IPA | 8.5% |
| Operation Flintlock Peanut Butter | Listermann Brewing Company | American Stout | 6.0% |
| Operation Freedom | Northern Monk | American IPA | |
| Operation Plowshare | Urban Artifact | Fruit and Field Beer | 7.7% |
| Operation: Nighthawk | The Fermentorium | | 8.5% |
| Operis | Four Winds Brewing | Saison | 7.0% |
| Opgebokt! | Van Moll | Doppelbock | 7.5% |
| Ophion (Vanilla) | Mortalis | | |
| Opia | Hair of the Dog Brewing Company | American Imperial Stout | 12.0% |