Bedrift O - Bekkelaget
- Optimert AS
- Olefondet AS
- Owsiany
- Oxmeis AS
- Orakel AS
- Osp AS
- Oka AS
- Overbird AS
- Ocius AS
- Onsirat AS
- Omrani Music
- Oscar Jøraandstad
- Oslo Sveisemek
- Oslo Malerbedrift AS
- Odd Hesselberg
- Ohoh Holding AS
- Ogo Invest AS
- Opplæring Nitschkes
- Olav Investerer AS
- Olav Jetlund AS
- Othmans Import
- Ovesen Musikk
- Orset Sport
- Office Care AS
- Oksdøl Invest AS
- Objektiv Partner AS
- Ok Maritime AS
- Olav Haddeland
- Ola Heining
- Obabo Holding AS
- Oslo Terrengsykkelcup
- Oslo Bedriftsidrettskrets
- Oslo Skytterkrets
- Oslo Skikrets
- Oslo Kfum
- Oobro Fossen
- Oslo Kiteskole
- Osloidrettens Studieforbund
- Osloidrettens Studieforbund
- Opat Holding AS
- Oslo Bandykrets
- Oslo Mood AS
- Onmii Trading AS
- Ogr Invest AS
- Ordo Investeringsselskap AS
- Oslo Friidrettskrets
- Odajakob Invest AS
- Oxford Recruitment
- Ormøy Menighet
- Oslo Idrettskrets
- Oslo Fotballkrets
- Olav Vhile
- Ohb Trading AS
- Offshore Piping AS
- Oko Taxi
- Oug Holding AS
- Ohm El.installasjon AS
- Oslo Container Terminal AS
- Odd Hesselberg Design
- Olaf Ek Jacobsen
- Oslo Hage Graveservice AS
- Odd Henning Arntzen
- Oslo Byggeadministrasjon Invest AS
- Oberst Invest AS Tvangsavviklingsbo
- Oberst Invest AS Tvangsavviklingsbo
- Oslo Perl Mongers
- Oppussingtjenester Marcin Kubas
- Oslo Malermesterlaugs Dameforening
- Ole Ragnar Walsig
- Ose Tech Consult
- Oslo Prop House AS
- Ole Marius Christiansen AS
- Oss på Hjørnet AS
- Oslo Svømmekrets Kretskontor
- Oddane Marius Maslahat
- Oscar Valland Lund
- Odd Arvid Strømstad
- Otto Bock Scandinavia
- Oslo Cheer Klubb Galaxy
- Oslo Cheer Klubb Galaxy
- Olaf A B Styrmoe Enk
- Oddfrid Ropstad Costume Design
- Osiris Robert Marc Friedman
- Osa Ie Anleggsavdelingen Majorstua
- Orbis Investment Advisory Limited
- Ole Deviks vei 48 AS
- Olsen Facit Consult Elisabeth
- Oslo og Akershus Basketballkrets
- Oslo og Akershus Rytterkrets
- Oslo Vintage Mari Kjendsli
- Oslo Fremskrittsparti Bydelslag Nordstrand
- OBS-Vær Varsom Per Helbostad
- Olaf A B Styrmoe Holding AS
- Oleg Football Development Coaching Olegs
- Oacm Ocean Alliance Conservation Member
- Olaf Billes Legat for Blomsterhagens Utvikling
- Otto Bock Scandinavia Norsk Avdeling Av
- Oaek - Oslo Akershus Elektro og Klima AS