Firma O - Grefsen
- Optisalm AS
- Operations AS
- Optimo AS
- Ojals AS
- Ojan AS
- Oddevald Bygg AS
- Oddevald Holding AS
- Oddpictures Filmproductions AS
- Oslo Limousinservice AS
- Olaskjær Bryggeforening
- Oslo Psykoterapipraksis AS
- Obn Eiendom AS
- Ottesen Bygg AS
- Oslo Tekstilservice AS
- Oslo Sangerforum
- Oslo Sangerforum
- Oskar Lie
- Obuskovic Music
- Oslo Vinterfotball
- Ottersen Holding AS
- Ottersen Racing AS
- Oslo Skisenter AS
- Oslo Skisenter AS
- Oksana Loretzen
- O&V Bygg AS
- Ole Petter Haneborg
- Ole Andreas Olafsrud
- Odd Magne Hagen
- Oslo Juristfirma Ludvigsen
- Oslo Blindes Helsesportlag
- Oslo Hvite Bånd
- Oslo Blindes Helsesportlag
- Orry-San Holding AS
- Ole Jacob Nilsen
- Oslo Kfum Sanitet
- Originalkopi Sveinung Sudbø
- Olivia Kensland Design
- Osterhus Valborg Anna K
- Oslo og Omegn Fluefiskere
- Oslo HiFi Montering AS Tvangsavviklingsbo
- Oslo HiFi Montering AS Tvangsavviklingsbo
- Olf Consult & Invest AS
- Offbeat Trading Granli Høgalmen
- Oslo Bærum Trafikkskole Raymond Smenes
- Othilie Tonnings vei 8 B Bolig
- Oslo Sporveiers Arbeiderforening (Osa) Velferd Trikken
- Oslo Lillomarka Krets Av Norges Speiderforbund
- Olims Sincere Food To the People Mathias
- Omsorgsboliger - Boliger for Psykisk Utvh.og Funksjonsh.
- Olav A Kristoffersen Eftf Jan P Kristoff