Bedrift O - Bjerke
- Obara AS
- Objektservice AS
- Ottar Nesje
- Online Tours AS
- Opensky Consulting AS
- Opensky Invest AS
- Oslo Byggdrift AS
- Oslo Membranservice AS
- Oslo Glassindustri AS
- Oslo Data AS
- Orelia Barnehage
- Oslo Containerservice AS
- Olsen Kompetanse
- Oppdretter Buzdimirovic
- Oleg Cherkasov
- Oslo Gateteam
- Op Bygg AS
- Olerud Music
- Oskar Josef Oskarsson
- Ole Eiliv Løstegaard
- Oleg Andreetvich Seidomitov
- Oslo Bygg T AS
- Ovidiu-Danut Huminiuc Konkursbo
- Oana-Andreea Agudaru-Hultoana
- Ovidiu-Danut Huminiuc Konkursbo
- Orphans Foundation Of Norway
- Oak Tree Atlas Holding AS
- Oslo Transport Services Limited
- Oslo Arkitektenes Rinkbandy Lag
- Oslo og Akershus Travforbund
- Oles Malerservice Ole Tommy Sand
- Omguldal Consult Odd Magnus Guldal
- Ofori-Amanfo Transport And Delivery
- Orb Photography Av Olve Reiersgård Bredesen
- Oslo Renhold Service Alejandro Francisco Peres Gonzales