 | Ø.ANTONSEN AS | 964377111 | BERGEN |
| O A SANNE AS | 932521806 | MOLDE |
| OBAS ØST AS | 983805183 | DRAMMEN |
| OBAS VEST AS | 960018095 | DRAMMEN |
| OBB AS | 921230125 | BJØRNAFJORDEN |
| OB BRENDEMOEN AS | 965678492 | NORD-FRON |
| ØBE AS | 921863993 | BÆRUM |
| OBERRAUTER BYGG OG SPRENGNING AS | 915540813 | VESTBY |
| OBOS PROSJEKT AS | 931536532 | OSLO |
| OBRON AS | 999536492 | AURE |
| OBRON ØST AS | 998667852 | STANGE |
| ØB RØR AS | 936606040 | ØRSTA |
| ØB-TAK AS | 971072830 | OSLO |
| O.B. Wiik A/S | 934122224 | LILLESTRØM |
| OCAB AS | 916326211 | BÆRUM |
| ODAL BYGG AS | 931933795 | SØR-ODAL |
| ODAL ENTREPRENØR AS | 994449826 | SØR-ODAL |
| O D BYGG AS | 924661399 | HØYANGER |
| ODD ARNE AARSTAD | 977105579 | KONGSVINGER |
| ODD BARTHO-HANSEN & SØNNER AS | 955499697 | FÆRDER |
| ODD BJERKEVOLL AS | 942654723 | VESTNES |
| ODD EINAR KNE AS | 974904535 | STEINKJER |
| ODD ERLING LØVØY | 968174835 | HERØY (MØRE OG ROMSDAL) |
| ODD FARMEN AS | 925415693 | LARVIK |
| ODD HAGERUD AS | 976018192 | EIDSKOG |
| ODD HANSEN AS | 971090715 | HAUGESUND |
| ODDMUND GROVEN AS | 923627804 | ØRLAND |
| ODD SMÅGE AS | 954505170 | AUKRA |
| ODD STENSVOLD AS | 995680084 | LARVIK |
| ODDVAR MELING AS | 980151794 | STAVANGER |
| ODDVAR NYBROT AUTORISERT RØRLEGGERFIRMA | 930232882 | BJØRNAFJORDEN |
| ODDVAR ØYGARD AS | 985793581 | ÅL |
| ØDEGAARD ANLEGG AS | 992170905 | BRØNNØY |
| ØDEGAARD OG STERTEN AS | 997907116 | BÆRUM |
| ØDEGÅRD BYGG OG MASKIN AS | 919232773 | LUSTER |
| ODIN BRANNTEKNIKK AS | 922957398 | OSLO |
| ODIN BYGG AS | 982592992 | BERGEN |
| ODLAND AS | 914419700 | HÅ |
| O DRAGE ENTREPRENØR AS | 963505329 | SUNNFJORD |
| OEG TEGNEKONTOR AS | 988380717 | TRONDHEIM |
| ØEI AS | 812508032 | OSLO |
| OEN AS | 944328785 | BERGEN |
| ØEN & HAUGSTAD AS | 988008885 | HÅ |
| ØEN HYTTEBYGG AS | 892353662 | HOL |
| ØEN KULDETEKNIKK AS | 980838277 | VOLDA |
| OFOTEN MASKIN AS | 974492032 | NARVIK |
| OFOTEN MEK AS | 924426993 | NARVIK |
| OFOTEN RØR AS | 968277898 | NARVIK |
| ØGLÆND-NORHEIM AS | 990696659 | SANDNES |
| O.HANSEN & SØNNER A/S | 945937513 | KARMØY |