Bedrift O - Hvalstad
- Oltedal A/S
- Optivinst AS
- Oppstrøms AS
- Oppussingstjenester Nasiadka
- Oda Lockert
- Optimist Invest AS
- Ordentlig Gym AS
- OPUS Systemer AS
- OSF Brusetkollen
- Oslo Backline
- Olstad Mxandrine Profilering
- Oralkirurg Modassar Amin
- Oslo Industrial Logic AS
- On Mol Holding AS
- Olsen Agentur AS Sigmund
- Ortoped Anders Lyche Svindland
- Oslo Politiets Selvbyggerlag Nr 7