 | 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 |
| 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 BRUGRAND AS | 934921046 | LÆRDAL |
| OSKAR JOHANSEN AS | 971082879 | NOTODDEN |
| OSKAR OG TORMOD WIKE AS | 930705462 | TØNSBERG |
| ØS KONSULT AS | 989193139 | ASKER |
| OSLAND MASKIN AS | 912309142 | KLEPP |
| OSLO-AKERSHUS RØRLEGGERBEDRIFT AS | 994920790 | OSLO |
| OSLO BAD AS | 995797267 | OSLO |
| OSLO BAD & FLIS AS | 931298739 | OSLO |
| OSLO BAD & RENOVERING AS | 813498952 | OSLO |
| OSLO BLIKKENSLAGERMESTER AS | 922541639 | OSLO |
| OSLO BYGGASSISTANSE AS | 916093632 | NORDRE FOLLO |
| OSLO BYGGENTREPRENØR AS | 950030119 | OSLO |
| OSLO-BYGGENTREPRENØR AS | 921331932 | ULLENSAKER |
| OSLO BYGGMESTER SERVICE DRIFT AS | 932691175 | SØR-ODAL |
| OSLO BYGG OG EIENDOM AS | 976567846 | OSLO |
| OSLO BYGG OG MONTASJESERVICE AS | 925015008 | OSLO |
| OSLO BYGG OG RESTAURERING AS | 934179226 | BÆRUM |
| OSLO BYGGREHAB AS | 917016283 | OSLO |
| OSLO ELECTRO COMPANY AS | 963983549 | OSLO |
| OSLO ELEKTRISKE AS | 961732778 | OSLO |
| OSLO ENGINEERING AS | 924454296 | OSLO |
| OSLO ENTREPRENØR AS | 964676607 | OSLO |
| OSLO ENTREPRENØRBEDRIFT AS | 913155637 | OSLO |
| OSLOFJORDEN BYGG AS | 976465415 | RÅDE |
| OSLOFJORD VARME AS | 979994265 | BÆRUM |
| OSLO & FOLLO BYGGTJENESTER AS | 923135154 | ÅS |
| OSLO GLASS OG RØRLEGGERSERVICE AS | 936968694 | LILLESTRØM |
| OSLO GRAVETEKNIKK AS | 931834606 | ULLENSAKER |
| OSLO KJØL & KLIMA AS | 912015688 | LILLESTRØM |
| OSLO KOMMUNE EIENDOMS- OG BYFORNYELSESETATEN | 874780782 | OSLO |
| OSLO MALERMESTER FORRETNING AS | 915883060 | OSLO |
| OSLO MURMESTERBEDRIFT AS | 998530261 | OSLO |
| OSLO OG ROMERIKE RØRLEGGERBEDRIFT AS | 927551365 | LILLESTRØM |
| OSLO OPPMÅLING AS | 923730796 | OSLO |
| OSLO OPPUSSING AS | 919636939 | OSLO |
| OSLO PLUMBING AS | 921208383 | OSLO |
| OSLO PROSJEKT AS | 933846296 | OSLO |
| OSLO PROSJEKT AS | 933787575 | OSLO |
| OSLO PROSJEKTBYGG AS | 911811073 | OSLO |
| OSLO RØRENTREPRENØR AS | 934385179 | OSLO |
| OSLO RØRLEGGER & ENTREPRENØRBEDRIFT AS | 991310894 | LØRENSKOG |
| OSLO RØR OG VARME AS | 923888225 | OSLO |
| OSLO RØR & SANITÆR AS | 993527270 | OSLO |
| OSLO RØRSERVICE AS | 921501315 | INDRE ØSTFOLD |
| OSLO RØRTEKNIKK AS | 919827688 | ASKER |
| OSLO RØRTEKNIKK TOMAS VASCILA | 913568397 | ASKER |
| OSLO SNEKKER AS | 918089462 | OSLO |
| OSLOSNEKKEREN AS | 918536450 | OSLO |
| OSLO TEGL & PUSS AS | 981568850 | OSLO |
| OSLO TERMOGRAFI OG BYGGTEKNIKK AS | 812166352 | NITTEDAL |
| OSLOTRE AS | 827301752 | OSLO |
| OSLO VEDLIKEHOLD OG SNEKKERSERVICE AS | 993138932 | LILLESTRØM |
| OSLO VEST REHABILITERING AS | 979677138 | NORDRE FOLLO |
| OSLO & VIKEN RØRLEGGER AS | 926611917 | OSLO |
| OSLO VVS SERVICE AS | 957810950 | OSLO |
| OSLO WORKS AS | 916528353 | OSLO |
| OS MASKINSERVICE AS | 918018697 | BJØRNAFJORDEN |
| OSM BYGG AS | 925147869 | DRAMMEN |
| OSMUND NORUM AS | 966812052 | LINDESNES |
| OSPAS AS | 985442428 | RANA |
| O. STABELL ELEKTRISKE AS | 998541298 | OSLO |
| ØST ANLEGGSSERVICE AS | 936403670 | NANNESTAD |
| ØSTAVIND ARKITEKTER AS | 976060180 | MOSS |
| ØST BYGG & MUR AS | 931817493 | SØR-AURDAL |
| ØSTCONSULT AS | 914215838 | FREDRIKSTAD |
| O.S TEKNIKK AS | 915156037 | INDRE FOSEN |
| ØST ELEKTRO AS | 921707959 | NANNESTAD |
| ØSTENGEN & BERGO AS | 976582705 | OSLO |