 | OLE M DOBLOUG | 979644132 | RINGSAKER |
| OLE OG TORES RØRSERVICE AS | 987289597 | KRAGERØ |
| OLE P. BAKKEN AS | 928195678 | HOLTÅLEN |
| OLE PETTER STRØMME AS | 988283142 | VINJE |
| OLE RISTE BYGGEVIRKSOMHET | 970058362 | FJORD |
| OLE SIVERTSEN AS | 817842712 | TRONDHEIM |
| OLE TERJE JOSDAL | 977099544 | SIRDAL |
| OLE TOM EGER FJELLSPRENGING AS | 997104676 | TØNSBERG |
| O. LILLEÅS GRUSTAK/TRANSPORT | 990698651 | ORKLAND |
| OLIMB ANLEGG AS | 997409841 | RÅDE |
| OLIMB RØRFORNYING AS | 997447018 | RÅDE |
| OLIVA PARK AS | 920721095 | SARPSBORG |
| O.Løkken A/S | 931515829 | TRONDHEIM |
| OLS1VVS AS | 820951522 | ØVRE EIKER |
| OLSENBYGG GRIMSTAD AS | 998339898 | GRIMSTAD |
| OLSEN MASKINENTREPRENØR AS | 915939686 | BJØRNAFJORDEN |
| OLSEN MASKIN & TRANSPORT AS | 919898690 | DØNNA |
| OLSEN RØRLEGGERSERVICE AS | 927532751 | STANGE |
| OLSET KSU AS | 821996112 | KRISTIANSUND |
| OL TO VVS AS | 983232108 | VENNESLA |
| OLYMPUS VVS AS | 823874642 | LØRENSKOG |
| OMA MASKIN | 861758532 | TIME |
| OM BAKKEN BYGG AS | 966707496 | NORD-FRON |
| O&M BYGG AS | 922083134 | BERGEN |
| OMC BYGG AS | 998360617 | BERGEN |
| OMDAL BETONG AS | 912772381 | LILLESAND |
| OMEGA 365 AREAL AS | 986930264 | VINDAFJORD |
| OMEGA AKERHOLDT AS | 913130529 | ASKER |
| OMEGA TDS AS | 991091270 | TØNSBERG |
| OMEGA VVS BERGER | 922809488 | ASKER |
| ØMF ASKER RINGERIKE AS | 830220852 | ASKER |
| ØMF EVENSEN & EVENSEN AS | 984958552 | LILLEHAMMER |
| ØMF HAMAR AS | 930220760 | HAMAR |
| ØMF NEDRE ROMERIKE OSLO AS | 916053983 | NITTEDAL |
| ØMF ØSTFOLD AS | 930220841 | MOSS |
| ØMF ROMERIKE KONGSVINGER AS | 911669668 | KONGSVINGER |
| ØMF WITO AS | 884587832 | EIDSKOG |
| OMKRI PLAN & ARKITEKTUR AS | 932155931 | TØNSBERG |
| OMLAND MASKIN AS | 990808333 | KVINESDAL |
| OMLID AS | 928821595 | EIGERSUND |
| OMMEDAL & SØNNER AS | 934033302 | TØNSBERG |
| OM MILJØTEKNIKK AS | 923380701 | BERGEN |
| OMT BBL | 948054353 | NARVIK |
| O. MYDLAND MASKIN AS | 984454945 | SOKNDAL |
| ONARHEIM AS | 946471623 | OSLO |
| ON ARKITEKTER OG INGENIØRER AS | 992619295 | ORKLAND |
| ONECO ELEKTRO AS | 996669173 | OSLO |
| ONECO MOBIL AS | 925894168 | OSLO |
| ONECO NETWORKS AS | 987210001 | OSLO |
| Ø. NORDBERG BYGGPROSJEKTERING | 889468742 | SARPSBORG |