| Ortoped Og Idrettslege Mette Andersen AS | Tromsø | 2023 |
| Ortopedersen AS | Rendalen | 2025 |
| Ortopedi Vest AS | Bergen | 2000 |
| Ortopedia AS | Drammen | 2007 |
| Ortopedisenteret AS | Oslo | 2006 |
| Ortopedisk Medisin Nord AS | Bodø | 2011 |
| Ortopedisk Viken AS | Oslo | 2020 |
| Ortoptist Klinikken AS | Bekkestua | 2024 |
| Ortoserv AS | Oslo | 2002 |
| Ortour Limited Nuf | Stavanger | 2009 |
| Os Allmennpraksis Da | Os | 2001 |
| Os Allè 19B AS | Halden | 2014 |
| Os Allè Tannklinikk AS | Halden | 2014 |
| Os Manuellterapi & Fysioterapi AS | Os | 2009 |
| Os Terapihund AS | Hagavik | 2023 |
| Osa AS | Bergen | 2005 |
| Osan Medical AS | Terråk | 2022 |
| Oscar Ohene Asante Holding AS | Oslo | 2019 |
| Osh Holding AS | Rypefjord | 2021 |
| Oslo Akutten AS | Oslo | 1985 |
| Oslo Ashihara Karate Og Fysioterapi AS | Oslo | 2015 |
| Oslo Barneklinikk AS | Oslo | 2015 |
| Oslo Beauty Center AS | Oslo | 2020 |
| Oslo City Legesenter AS | Oslo | 1990 |
| Oslo Dent AS | Oslo | 2023 |
| Oslo Dermatologi AS | Oslo | 2021 |
| Oslo Endodontisenter AS | Oslo | 2016 |
| Oslo Fot-Ankel Kirurgiske Senter AS | Oslo | 2021 |
| Oslo Fotterapeutklinikk AS | Oslo | 2024 |
| Oslo Gastroklinikk AS | Oslo | 2019 |
| Oslo Gynekologiske Klinikk AS | Oslo | 1994 |
| Oslo Health Clinic, Norsk Nevrokirurgisk, Allmenmedisinsk Og Idrettsmedisinsk Senter AS | Oslo | 2014 |
| Oslo Hjerteklinikk AS | Oslo | 2007 |
| Oslo Hjertesenter AS | Oslo | 2007 |
| Oslo Hodepineklinikk AS | Oslo | 2017 |
| Oslo Hodepinesenter AS | Oslo | 1998 |
| Oslo Hud Og Laserklinikk AS | Oslo | 2016 |
| Oslo Hudlegeklinikk AS | Oslo | 2011 |
| Oslo Hudlegekontor AS | Oslo | 2016 |
| Oslo Hudlegesenter AS | Oslo | 2012 |
| Oslo Implantatsenter AS | Oslo | 2008 |
| Oslo Jordmor Og Kvinnesenter AS | Oslo | 2012 |
| Oslo Jordmor Og Ultralydklinikk AS | Oslo | 2014 |
| Oslo Kardiologi AS | Oslo | 2020 |
| Oslo Kjeveortopedi Da | Oslo | 2009 |
| Oslo Laserklinikk AS | Oslo | 2017 |
| Oslo Logopedene AS | Oslo | 2014 |
| Oslo Lungelege AS | Oslo | 2020 |
| Oslo Massasje AS | Oslo | 2009 |
| Oslo Medical Center AS | Oslo | 2012 |
| Oslo Mediq AS | Oslo | 2023 |
| Oslo Medisinske Senter AS | Oslo | 2021 |
| Oslo Naprapatklinikk AS | Oslo | 2012 |
| Oslo Nevro AS | Oslo | 2014 |
| Oslo Nevrologi Senter AS | Oslo | 2015 |
| Oslo Oral Kirurg AS | Oslo | 2025 |
| Oslo Osteopati Heidi Reenskaug AS | Oslo | 2016 |
| Oslo Osteopati Og Akupunkturklinikk AS | Oslo | 2018 |
| Oslo Private Legevakt AS | Oslo | 2023 |
| Oslo Privatklinikk AS | Oslo | 2013 |
| Oslo Produksjon & Tjenester AS | Oslo | 1991 |
| Oslo Psykologkontor AS | Oslo | 2025 |
| Oslo Sanitetsforening Brusetkollen AS | Hvalstad | 2008 |
| Oslo Sentrum Tannklinikk AS | Oslo | 2024 |
| Oslo Smerteklinikk AS | Oslo | 1995 |
| Oslo Spine AS | Oslo | 2020 |
| Oslo Syn AS | Oslo | 2024 |
| Oslo Tannlege AS | Oslo | 2015 |
| Oslo Tannlegesenter AS | Oslo | 2012 |
| Oslo Tannlegesenter Og Tannlegevakt AS | Oslo | 2015 |
| Oslo Tannlegevakt Oslo AS | Oslo | 2008 |
| Oslo Tannmedisin AS | Asker | 2006 |
| Oslo Tannregulering AS | Oslo | 2010 |
| Oslo Tannteknikk Og Estetikk AS | Oslo | 2016 |
| Oslo Trenings Og Fysiologiske Testsenter AS | Oslo | 2019 |
| Oslo Urologiske Klinikk AS | Høvik | 2023 |
| Oslo Øre Nese Hals AS | Oslo | 2006 |
| Oslo Øresenter AS | Oslo | 2026 |
| Oslo Øst Tannregulering AS | Oslo | 2025 |
| Oslocity Tannlegesenter 1 AS | Oslo | 2015 |
| Oslocity Tannlegesenter AS | Oslo | 2024 |
| Oslofjordklinikken AS | Sandvika | 2007 |
| Oslofjordklinikken Vest AS | Sandnes | 2014 |
| Oslogynekologene AS | Oslo | 2014 |
| Oslohandcenter AS | Oslo | 2016 |
| Oslokollega Gruppen AS | Oslo | 1966 |
| Oslokollega Karriere AS | Oslo | 2021 |
| Oslokollega Utvikling AS | Oslo | 2021 |
| Osloperio AS | Oslo | 2026 |
| Oss-To Invest AS | Trondheim | 2023 |
| Ossum Legetjeneste AS | Hønefoss | 2005 |
| Ostapchuk Holding & Consult AS | Fredrikstad | 2026 |
| Ostara Helse AS | Porsgrunn | 2023 |
| Osteo Consult AS | Halden | 2002 |
| Osteomarcussen AS | Oslo | 2021 |
| Osteopat Elisabet AS | Alta | 2020 |
| Osteopat Elise AS | Oslo | 2025 |
| Osteopat Helene Victoria Ausland AS | Oslo | 2020 |
| Osteopat Marianne Johansen AS | Alta | 2022 |
| Osteopati Jøsendal AS | Oslo | 2025 |