Bedrift O - Tåsen
- Ocon AS
- Outcast AS
- Ooeo AS
- Orohena AS
- Oxymoron AS
- Ochrino AS
- Ontrack Management AS
- Ocd Gjeruldsen AS
- Oslofjorden Badmintonkrets
- Olea Björk
- Oshrat Haaland
- Onarheim Records
- Olufsen Imedia
- Ottosen Consulting
- Oleksandr Parasiuk
- Oksana Vishchyk
- Oleksii Postolnyi
- Oleksii Parasiuk
- Olga Schmedling
- Oleksandr Mozghovyi
- Oslofjorden Badmintonkrets
- Orhagen Plastikkirurgi
- Oleksandr Shkodych
- Oddgeir Thune
- Olha Patsuryna
- Oslo Analytica AS
- Oddvar Ringstad
- Orhagen Plastikkirurgi AS
- Ole Reigstad
- Oslo Treklatreklubb
- Ole Reigstad
- Oleh Preor
- Olena Bozhenko
- Olesia Bohun
- Onesti Products AS
- Olastranda Velforening
- Oker Arkitektur AS
- Olborg Holding AS
- Ormstrup Holding AS
- Ocnn 2 AS
- Opheim Consulting
- Ong Kundeservice
- Oslodugnad - Nordbrenden
- Oslo Interiørmontasje
- Omhr Tech AS
- Orkidé Service Alokla
- O.T Holding AS
- Oslo Malermester Forretning AS
- Odd Røberg Eiendomsforvaltning
- Oslo Pickleball Club
- Oslo Pickleball Club
- Octographic Morten Ødegaard
- Ole Kristian Kogstad
- Oslo Sports Agency AS
- O. Mysterud Eiendom AS
- O. Moen Invest
- Oda Balke Fjellang
- Opheim Limousine Service
- Oppussing-Bygg Skapski
- Ottar Annfelt Moe
- Ole-Christian L. Brun
- Otero Bislet Massasje Lucia
- Oslo Birder Simon Rix
- Oslo VVS & Bad AS
- Oversetter Eva Marie Håland
- Ortoped E.B. Claudi
- Oppussingskonsulenten Irene Birgitte Wenaas
- Oppegaard Fysioterapi og Trening
- Ohifs Dameforenings Boliger for Eldre
- Olav Helland Foto og Formidling
- Oriens Forlag Notto R Thelle
- Omsorgsboliger - Boliger for Psykisk Utvh.og Funksjonsh.
- Oslo Kommune Bydel 8 nordre Aker Bergsalleen Bolig