| O! Gold Light Beer | Upstream Brewing Old Market | Light Lager | 3.8% |
| O'ambic | Craftwork | Lambic | 6.0% |
| O'Brians 25th Anniversary Blend | The Lost Abbey | American Strong Ale | 13.5% |
| O'Briens 20th Anniversary Blend | The Lost Abbey | American Strong Ale | 13.5% |
| O'Doyle Rules | Perennial Artisan Ales | American Imperial Stout | 13.2% |
| O'Hanraha-hanrahan | Pomona Island | Gose | 5.5% |
| O'Hara's Barrel Aged Irish Stout | Carlow Brewing Company | Irish Dry Stout | 8.1% |
| O'Hara's Celtic Stout | Carlow Brewing Company | American Stout | 4.3% |
| O'Hara's Irish Pale Ale | Carlow Brewing Company | American Pale Ale | 5.2% |
| O'Hara's Irish Red | Carlow Brewing Company | Irish Red Ale | 4.3% |
| O'Hara's Irish Stout | Carlow Brewing Company | Irish Dry Stout | 4.3% |
| O'Hara's Leann Folláin | Carlow Brewing Company | Irish Dry Stout | 6.0% |
| O'Hara's Leann Folláin | O'Hara's Brewery | | 6.0% |
| O'Malley's IPA | Weston Brewing Company | American IPA | 7.5% |
| O'Malley's Irish Cream Ale | Weston Brewing Company | Cream Ale | |