 | NUNO ARKITEKTUR AS | 942826400 | OSLO |
| NUPEN AS | 916067623 | HARSTAD |
| NVG RØR AS | 928335704 | NES |
| NYBOLOFT ENTREPRENØR AS | 985224439 | HAMMERFEST |
| NYBYGGERN AS | 982044537 | LYNGDAL |
| NYDAHL ANLEGG AS | 915199739 | HAMAR |
| NYDALS MASKINSTASJON AS | 853097012 | HARSTAD |
| NYE ARKEL ROMERIKE AS | 931327003 | RÆLINGEN |
| NYE MONTASJESERVICE AS | 931605593 | ASKER |
| NYE NORDLANDTAK AS | 932405342 | VEFSN |
| NYGÅRD ENTREPRENØR AS | 925231363 | ENGERDAL |
| NYGÅRD TAK AS | 990483582 | SVEIO |
| NYHEIM BYGG OG ANLEGG AS | 933902420 | ALSTAHAUG |
| Ny-Hus AS | 931120875 | BERGEN |
| NYLAND BYGGEADMINISTRASJON AS | 934767403 | SANDNES |
| NYMARK VVS AS | 933916545 | SANDNES |
| NYMOE ELEKTRO AS | 986673768 | ALTA |
| NYPAN HAGE & ANLEGG AS | 985264392 | TRONDHEIM |
| NYRØ TEKNOLOGI AS | 924403152 | ØRSTA |
| NYSTED AS | 976074580 | BALSFJORD |
| NYSTØ BYGG AS | 833794302 | KONGSVINGER |
| NYSTØL & FAGERHOL AS | 981463579 | VANYLVEN |
| NY STRUKTUR AS | 918294112 | OSLO |
| NYTTBYGG AS | 913359771 | SARPSBORG |
| NYTT PROSJEKT AS | 974389657 | OSLO |
| NYVOLD INSTALLASJON AS | 957724787 | OPPDAL |
| NYVOLL CONSULT AS | 993172537 | NITTEDAL |
| NZ RØRSERVICE AS | 922129800 | LILLESTRØM |
| Ø.ANTONSEN AS | 964377111 | BERGEN |
| O A SANNE AS | 932521806 | MOLDE |
| OBAS ENTREPRENØR AS | 960018095 | BERGEN |
| OBB AS | 921230125 | BJØRNAFJORDEN |
| OB BRENDEMOEN AS | 965678492 | NORD-FRON |
| ØBE AS | 921863993 | ULLENSAKER |
| OBERRAUTER BYGG OG SPRENGNING AS | 915540813 | VESTBY |
| OBOS BLOCK WATNE ENTREPRENØR AS | 930061212 | OSLO |
| OBOS PROSJEKT AS | 931536532 | OSLO |
| OBRON GRUPPEN AS | 998300665 | TRONDHEIM |
| ØB RØR AS | 936606040 | ØRSTA |
| ØB-TAK AS | 971072830 | OSLO |
| OCAB AS | 916326211 | BÆRUM |
| ODAL ANLEGGSDRIFT AS | 932475057 | NORD-ODAL |
| 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 HEIBERG AS | 984556128 | HORTEN |
| ODD MATHISEN AS | 979924410 | ALTA |
| ODDMUND GROVEN AS | 923627804 | ØRLAND |
| Odd-Petter Hosen AS | 947714821 | ÅFJORD |
| ODD SMÅGE AS | 954505170 | AUKRA |
| ODD STENSVOLD AS | 995680084 | LARVIK |
| ODDVAR MELING AS | 980151794 | STAVANGER |
| ODDVAR ØYGARD AS | 985793581 | ÅL |
| ØDEGAARD ANLEGG AS | 992170905 | BRØNNØY |
| ØDEGAARD OG STERTEN AS | 997907116 | BÆRUM |
| ØDEGÅRD BYGG OG MASKIN AS | 919232773 | LUSTER |
| ØDEGÅRDENS PLANTESKOLE OG UTEMILJØ AS | 983136613 | GRIMSTAD |
| ODIN BRANNTEKNIKK AS | 922957398 | OSLO |
| ODIN BYGG AS | 982592992 | BERGEN |
| ODLAND AS | 914419700 | HÅ |
| O DRAGE ENTREPRENØR AS | 963505329 | SUNNFJORD |
| ØEN & HAUGSTAD AS | 988008885 | HÅ |
| ØEN HYTTEBYGG AS | 892353662 | HOL |
| ØEN KULDETEKNIKK AS | 834263602 | VOLDA |
| OFFJORD-ENTREPRENØR AS | 932172798 | OSLO |
| OFOTEN MASKIN AS | 974492032 | NARVIK |
| OFOTEN MEK AS | 924426993 | NARVIK |
| OFOTEN RØR AS | 968277898 | NARVIK |
| O.HANSEN & SØNNER AS | 934235347 | KARMØY |
| Ø. HELLESØY RØRLEGGER SERVICE | 990118469 | BERGEN |
| OHNSTAD AS | 923363270 | LARVIK |
| ØIJORD & AANES ENTREPRENØRFORRETNING AS | 957749933 | RANA |
| ØISETH MONTASJE AS | 935096839 | KONGSVINGER |
| ØISTAD ELEKTRO AS | 988277231 | GRAN |
| ØISTEIN ASK ANDERSEN | 970335633 | SANDEFJORD |
| ØIVIND ÅSMANN | 968352113 | ULLENSAKER |
| ØIVIND BRÅTHEN AS | 966890967 | ØVRE EIKER |
| ØIVIND FJELD BYGG OG TØMRERMESTER AS | 982205492 | BÆRUM |
| ØIVIND LYSTAD AS | 936860478 | KRISTIANSUND |
| O J MILJETEIG AS | 938173605 | HAUGESUND |
| ØJ RØR AS | 914179165 | KRØDSHERAD |
| OK ANLEGG AS | 912697290 | VÅLER (ØSTFOLD) |
| OK ANLEGGSSERVICE AS | 984797540 | DRAMMEN |
| OK BAD AS | 992779926 | TIME |
| OK BYGG & ANLEGG AS | 928202720 | OVERHALLA |
| OK+ BYGG AS | 933108279 | BERGEN |
| ØK-BYGG AS | 924531215 | GRAN |
| OKER ARKITEKTUR AS | 976186419 | OSLO |
| OKKENHAUG ENTREPRENØR AS | 911851482 | LEVANGER |
| O K LIE AS | 982049741 | ØVRE EIKER |
| Ø.K MASKINDRIFT AS | 918697365 | ØSTRE TOTEN |
| ØKO AS | 924824484 | KRISTIANSAND |
| ØKO GRØNT AS | 979908431 | VINJE |