Bedrift O - Alfaset
- Ortus DA
- Ombh AS
- Only
- Onrail AS
- Oslo Expo
- Oslo Expo
- Oslo Veggdyrkontroll AS
- Oslo Anleggsbedrift AS
- Origo bygg AS
- Oslo Bilhjelp AS
- Oslo Entreprenørbedrift AS
- Oslo Byggfix AS
- Oslo Entreprenørbedrift AS
- Omega Installasjon AS
- Oslo Bilsalg AS
- Olena Perehniak
- Oslo Lifthavn AS
- Oslo Byggkontroll AS
- Oslo Bilpleie AS
- Oslo Murmesterbedrift AS
- Oslo Varebilspesialisten AS
- Oslo Bedriftsidrettslag
- Oslo Entreprenør AS
- Oslo Elektriske AS
- Oslo Entreprenør AS
- Oslo Stillasutleie AS
- Omb Hylle 1 AS
- Office Refreshment Systems
- Oslo-Akershus Rørleggerbedrift AS
- Oslo Lastebilservice (SjekkPunkt)
- Otto Bock Scandinavia
- Ole Deviks vei 48 AS
- Oslo Bolig og Næringsutvikling AS
- Ole Deviks vei 44 AS
- Ole Deviks vei 46 AS
- Oslo Tegl & Puss AS
- Olsen & Terra Transport Skandinavia AS
- Orlando Severino Do Nacimento Fortes