 | OLIMB RØRFORNYING AS | 997447018 | RÅDE |
| OLIVA PARK AS | 920721095 | SARPSBORG |
| O L KYTHE AS | 935252601 | VOSS |
| O.Løkken A/S | 931515829 | TRONDHEIM |
| OLS1 HOLDING AS | 920471129 | LINDESNES |
| OLS1VVS AS | 820951522 | DRAMMEN |
| OLSENBYGG GRIMSTAD AS | 998339898 | GRIMSTAD |
| OLSEN MASKIN & TRANSPORT AS | 919898690 | DØNNA |
| OLSEN RØRLEGGERSERVICE AS | 927532751 | LILLESTRØM |
| OLSET KSU AS | 821996112 | KRISTIANSUND |
| OL TO VVS AS | 983232108 | VENNESLA |
| OLYMPUS VVS AS | 823874642 | OSLO |
| OMA MASKIN | 861758532 | TIME |
| OM BAKKEN BYGG AS | 966707496 | NORD-FRON |
| O&M BYGG AS | 922083134 | BERGEN |
| OMDAL BETONG AS | 912772381 | LILLESAND |
| OMEGA 365 PROTEK AS | 980361330 | KARMØY |
| OMEGA AKERHOLDT AS | 913130529 | ASKER |
| OMEGA BYGG AS | 928978591 | TYSNES |
| OMEGA TDS AS | 991091270 | TØNSBERG |
| ØMF ASKER RINGERIKE AS | 830220852 | ASKER |
| ØMF EVENSEN & EVENSEN AS | 984958552 | LILLEHAMMER |
| ØMF HAMAR AS | 930220760 | HAMAR |
| ØMF ROMERIKE KONGSVINGER AS | 911669668 | KONGSVINGER |
| ØMF WITO AS | 884587832 | EIDSKOG |
| OMGI PRODUCTION AS | 927376695 | TØNSBERG |
| OMHU NORD AS | 933178528 | TROMSØ |
| OMKRI PLAN & ARKITEKTUR AS | 935229871 | TØNSBERG |
| OMLAND MASKIN AS | 990808333 | KVINESDAL |
| OMMEDAL & SØNNER AS | 934033302 | TØNSBERG |
| OM MILJØTEKNIKK AS | 923380701 | BERGEN |
| OMN BYGG AS | 935108160 | ÅLESUND |
| OM SIMONSEN MASKIN AS | 999568033 | MÅLSELV |
| OMT BYGG AS | 933497798 | SUNNFJORD |
| O. MYDLAND MASKIN AS | 984454945 | SOKNDAL |
| ONA CONSULTING AS | 936512585 | STAVANGER |
| ONARHEIM AS | 946471623 | OSLO |
| ON ARKITEKTER OG INGENIØRER AS | 992619295 | ORKLAND |
| ONECO ELEKTRO AS | 996669173 | OSLO |
| ONECO INFRA AS | 997768337 | ARENDAL |
| ONECO MOBIL AS | 925894168 | OSLO |
| ONECO NETWORKS AS | 987210001 | OSLO |
| Ø. NORDBERG BYGGPROSJEKTERING | 889468742 | SARPSBORG |
| O NØRSTEBØ & SØNN AS | 977046572 | NORE OG UVDAL |
| ONOS OLE NORDMO & SØNN AS | 950674237 | MÅLSELV |
| ONØY MASKINSTASJON AS | 923112065 | LURØY |
| ONSHUS BYGG AS | 931475150 | TRONDHEIM |
| ONSØIEN MASKIN AS | 996785475 | SKAUN |
| ONSØYHUS AS | 921660561 | FREDRIKSTAD |
| ONSØY RØR AS | 924329009 | FREDRIKSTAD |
| ONSØY RØRLEGGERBEDRIFT AS | 936722288 | FREDRIKSTAD |
| OPAK AS | 960816862 | OSLO |
| OP BYGG AS | 927472236 | OSLO |
| OPDAHL BYGG & REHAB AS | 927753324 | RINGERIKE |
| OPDAHL OG PETTERSEN ELEKTRO AS | 981112784 | PORSANGER |
| OPGÅRD GRUPPEN AS | 930601640 | ALTA |
| OPLAND MASKIN AS | 924824921 | MELHUS |
| OPPDAL MASKINKOMPANI AS | 915019463 | OPPDAL |
| OPPDAL VVS A/S | 947452517 | OPPDAL |
| OPPHEIM GRAVEMASKINSTASJON AS | 974533537 | VOSS |
| OPP KRAFTLEDNINGSTJENESTER AS | 986199381 | KRISTIANSAND |
| OPPLAND ELEKTRO AS | 986885358 | GAUSDAL |
| OPPLAND MUR OG FLIS AS | 984115121 | GJØVIK |
| OPPMÅLING AS | 933181707 | TRONDHEIM |
| OPPMÅLINGSTJENESTER AS | 915978150 | HARAM |
| OPPOPP AS | 926561847 | OSLO |
| OPPUSSING BERGEN AS | 921444729 | BERGEN |
| OPSAHL BOLIG AS | 982170834 | OSLO |
| OPSHAUG AS | 915031676 | STRANDA |
| OPTEO AS | 921554516 | SANDNES |
| OPTIBO UTBYGGING AS | 918623469 | BERGEN |
| OPTIMAL BRANNSIKKERHET AS | 929261879 | SKIEN |
| OPTIMAL ENTREPRENØR AS | 999169449 | FREDRIKSTAD |
| OPTIMAL KJØLING AS | 928603024 | NORDRE FOLLO |
| OPTIMAL RØRSERVICE AS | 919329114 | FROGN |
| OPTIMERA AS | 967013056 | OSLO |
| OPTIMERA BYGGSYSTEMER AS | 979658125 | OSLO |
| OPUS BERGEN AS | 921610602 | BERGEN |
| OPV CONSULTING AS | 917880697 | OSLO |
| ØRA ELEKTRO AS | 827026042 | SUNNDAL |
| ØRA RØR AS | 929473698 | SUNNDAL |
| ORIGO ARKITEKTGRUPPE AS | 943577374 | BERGEN |
| ORIGON AS | 933374580 | BÆRUM |
| ORION VAKTMESTERSERVICE AS | 983074200 | TRONDHEIM |
| ORKDAL VARME OG SANITÆR AS | 980557413 | ORKLAND |
| ORKLA LAFT AS | 986471219 | ORKLAND |
| ORKLA MARDAHL AS | 913684281 | ORKLAND |
| ORKLA STÅLKONSULT AS | 991235787 | ORKLAND |
| ØRLAND BYGGTJENESTER AS | 930878383 | ORKLAND |
| ORONA NORWAY AS | 984176503 | HAMAR |
| ORRA ENTREPRENØR AS | 927437961 | BJØRNAFJORDEN |
| ORSTAD RØR AS | 989067621 | KLEPP |
| ØRSTA VEDLIKEHALD AS | 958339216 | ØRSTA |
| OSA BYGG | 824386552 | GRIMSTAD |
| OSBYGG AS | 998256259 | BJØRNAFJORDEN |
| OSE AS | 994525174 | ØRSTA |
| OSE BYGG AS | 927409216 | KRISTIANSAND |
| OS ELEKTRO AS | 929975049 | BJØRNAFJORDEN |
| OS ENTREPRENØR AS | 986662707 | OS (INNLANDET) |
| OSKAR JOHANSEN AS | 971082879 | NOTODDEN |