| Brewery | Location |
|---|---|
| Omnipollo, Siren Craft Brew & Mike Bates | |
| On Tap Bistro & Brewery | San Diego, California |
| On Tour Brewing Company | Chicago, Illinois |
| ONCO Fermentations | Tully, New York |
| Oncore Brewery | Swanton |
| One Barrel Brewing | Madison |
| One Mile End | London |
| One Trick Pony | Lansing |
| One Well Brewery | Kalamazoo, MI |
| One World Brewing | Asheville, North Carolina |
| Onion Pub & Brewery | Lake Barrington, Illinois |
| Only Child | Northbrook, IL |
| Onopa Brewing | Milwaukee, Wisconsin |
| Onsala Hantverks Bryggeri | Onsala, Sweden |
| Oosteke Brouwers | Gavere |