| OSOhio-Kentucky Steel Corp. | Franklin | OH | — | ◇ UNVERIFIED |
| OMOhio Machined Products, Inc. | Holgate | OH | — | ◇ UNVERIFIED |
| OMOhio Match CO | Mancos | CO | — | ◇ UNVERIFIED |
| OMOhio Metal Technologies INC | Hebron | OH | — | ◇ UNVERIFIED |
| OSOhio Steel Industries (0145000318) | Pataskala | OH | — | ◇ UNVERIFIED |
| OSOhio Steel Industries, INC. | Summit Station | OH | — | ◇ UNVERIFIED |
| OVOhio Valley Fabrication and Energy INC. | Wheeling | WV | — | ◇ UNVERIFIED |
| OKOh Keys | Bethany | OK | — | ◇ UNVERIFIED |
| OPOh & Payne Intl. LLC. | Norcross | GA | — | ◇ UNVERIFIED |
| OIOiw, INC. | Pelham | AL | — | ◇ UNVERIFIED |
| OLOiw LLC | Oakdale | PA | — | ◇ UNVERIFIED |
| OKO & K American CORP. | Chicago | IL | — | ◇ UNVERIFIED |
| OO'keeffe's | Merced | CA | — | ◇ UNVERIFIED |
| OIO.k. Industries, INC. | Fostoria | OH | — | ◇ UNVERIFIED |
| OMOklahoma Millworks INC. | Guthrie | OK | — | ◇ UNVERIFIED |
| OBOld Bridge Metal Fabrication Inc. | Riverside | CA | — | ◇ UNVERIFIED |
| OOldcastle | Calverton | NY | — | ◇ UNVERIFIED |
| OOldcastle | Egg Harbor City | NJ | — | ◇ UNVERIFIED |
| OOldcastle | Nephi | UT | — | ◇ UNVERIFIED |
| OAOldcastle Azusa Dalou | Azusa | CA | — | ◇ UNVERIFIED |
| OFOldcastle Fort Worth Sylvania | Fort Worth | TX | — | ◇ UNVERIFIED |
| OHOldcastle Hector | Hector | MN | — | ◇ UNVERIFIED |
| OIOldcastle Infrastructure - Azusa 10th | Azusa | CA | — | ◇ UNVERIFIED |
| OIOldcastle Infrastructure - Azusa Dalou | Azusa | CA | — | ◇ UNVERIFIED |
| OIOldcastle Infrastructure / Poteau Facility | Poteau | OK | — | ◇ UNVERIFIED |
| OPOldcastle Precast | Olivehurst | CA | — | ◇ UNVERIFIED |
| OPOldcastle Precast INC | Canby | OR | — | ◇ UNVERIFIED |
| OVOldcastle Valdosta | Valdosta | GA | — | ◇ UNVERIFIED |
| OBOlde Bostonian | Dorchester | MA | — | ◇ UNVERIFIED |
| OGOldenburg Group INC | Kingsford | MI | — | ◇ UNVERIFIED |
| OSOld Sole Fabrication INC | Denver | CO | — | ◇ UNVERIFIED |
| OSOld South Fabricators L.l.c. | Lecompte | LA | — | ◇ UNVERIFIED |
| OTOld Town Fiberglass Dba Fiberglass Fab. | Orange | CA | — | ◇ UNVERIFIED |
| OSOlins Sheet Metal, INC. | Albany | GA | — | ◇ UNVERIFIED |
| OIOlivet International, INC. | Springdale | AR | — | ◇ UNVERIFIED |
| OCOlson & Company Steel | Fresno | CA | — | ◇ UNVERIFIED |
| OIOlson Iron & Stone Creations LLC | Elk River | MN | — | ◇ UNVERIFIED |
| OSOlson Steel | San Leandro | CA | — | ◇ UNVERIFIED |
| OCOlympia Chimney Supply, Incorporated | Scranton | PA | — | ◇ UNVERIFIED |
| OTOlympus Technologies Incorporated | Eugene | OR | — | ◇ UNVERIFIED |
| OOmco | Talladega | AL | — | ◇ UNVERIFIED |
| OFOmega Firm INC Dba Half Face Blades | San Diego | CA | — | ◇ UNVERIFIED |
| OPOmega Plastics, LLC | Erie | PA | — | ◇ UNVERIFIED |
| OSOmega Steel Products, INC | Jemison | AL | — | ◇ UNVERIFIED |
| OMO & M Fabricators, LLC | Pensacola | FL | — | ◇ UNVERIFIED |
| OIOmg, INC. Dba Hickman Engineered Systems | Arden | NC | — | ◇ UNVERIFIED |
| OPOmico Plastics INC | Owensboro | KY | — | ◇ UNVERIFIED |
| OCOmi Crane Systems INC | Royse City | TX | — | ◇ UNVERIFIED |
| OIOmnical, INC. | San Fernando | CA | — | ◇ UNVERIFIED |
| OCOmni CORP Ii | Saint Augustine | FL | — | ◇ UNVERIFIED |
| OOmniduct | Everett | WA | — | ◇ UNVERIFIED |
| OAOmniduct Arlington | Arlington | WA | — | ◇ UNVERIFIED |
| OAOmniduct Az, LLC | Phoenix | AZ | — | ◇ UNVERIFIED |
| OIOmni Industrial Services | Buffalo | WV | — | ◇ UNVERIFIED |
| OOmnimax | Gridley | IL | — | ◇ UNVERIFIED |
| OIOmnimax International, INC. | Ivyland | PA | — | ◇ UNVERIFIED |
| OIOmnimax International, LLC Dba Millennium Metals | Jacksonville | FL | — | ◇ UNVERIFIED |
 Omni Services | Falconer | NY | — | ◇ UNVERIFIED |
| OPOn-board Pmo, Corporation | Valley View | OH | — | ◇ UNVERIFIED |
| OMO'neal Manufacturing Services | Cedar Falls | IA | — | ◇ UNVERIFIED |
| OMO'neal Manufacturing Services | Indianapolis | IN | — | ◇ UNVERIFIED |
| OROne Rig Design LLC | Poland | ME | — | ◇ UNVERIFIED |
| OMOneto Metal Products CORP | Sacramento | CA | — | ◇ UNVERIFIED |
| OSOney Sheetmetal INC | Fort Myers | FL | — | ◇ UNVERIFIED |
| OCOn-site Custom Fabrication INC. | Hendersonville | TN | — | ◇ UNVERIFIED |
| OMOn-site Manufactured Buildings LLC | Branson | MO | — | ◇ UNVERIFIED |
| OTOn The Cutting Edge Inc. | Denver | CO | — | ◇ UNVERIFIED |
 On The Edge MFG, Inc | Kittanning | PA | — | ◇ UNVERIFIED |
| OTOn the Level Fabrication, LLC | Winder | GA | — | ◇ UNVERIFIED |
| OTOn Time Fab INC | Saint Joseph | KY | — | ◇ UNVERIFIED |
| OFOpc Fabrication and Equipment, INC. (fn) | Phoenix | AZ | — | ◇ UNVERIFIED |
| OTOp Tanks LLC | Pleasant View | UT | — | ◇ UNVERIFIED |
| OIOptiColor, Inc | Huntington Beach | CA | — | ◇ UNVERIFIED |
| OIOptinova-mle INC | Plymouth | MN | — | ◇ UNVERIFIED |
| OPOpus Plastics LLC | Somerville | NJ | — | ◇ UNVERIFIED |
| OCOrange County Erectors, INC. | Ontario | CA | — | ◇ UNVERIFIED |
| OSOrange State Steel | Bartow | FL | — | ◇ UNVERIFIED |
| OSOrange State Steel Construction, INC. | Riverview | FL | — | ◇ UNVERIFIED |
| OSOrange Steel Roofing Products | Orange | VA | — | ◇ UNVERIFIED |
| OCOrbis CORP | Madison Heights | MI | — | ◇ UNVERIFIED |
| OCOrbis Corporation | Mentor | OH | — | ◇ UNVERIFIED |
| OCOrbis Corporation | Wando | SC | — | ◇ UNVERIFIED |
| OCOrco Construction Supply | Bloomington | CA | — | ◇ UNVERIFIED |
| ODOreco Duct System INC | Baldwin Park | CA | — | ◇ UNVERIFIED |
| OAOregon Afscme Council 75 | Salem | OR | — | ◇ UNVERIFIED |
| OPOregon Pacific Structural Fabrication, LLC | Mulino | OR | — | ◇ UNVERIFIED |
| OPOregon Precision Industries INC | Eugene | OR | — | ◇ UNVERIFIED |
| OPOregon Precision Manufacturing INC | Sherwood | OR | — | ◇ UNVERIFIED |
| OVOregon Valley Greenhouses INC | Aurora | OR | — | ◇ UNVERIFIED |
| OSOreland Sheet Metal Inc | Huntingdon Valley | PA | — | ◇ UNVERIFIED |
| OTOrganic Transit INC. | Durham | NC | — | ◇ UNVERIFIED |
| OEOri Enterprises LLC | Price | UT | — | ◇ UNVERIFIED |
| OEOri Enterprises LLC | Wellington | UT | — | ◇ UNVERIFIED |
| OAOrion Asset Management Co., LLC | Akron | OH | — | ◇ UNVERIFIED |
| OCOrion Custom Boats | El Cajon | CA | — | ◇ UNVERIFIED |
| OPOrion Polymers LLC | Murfreesboro | TN | — | ◇ UNVERIFIED |
| OIOrlando Iron Works | Paterson | NJ | — | ◇ UNVERIFIED |
| OSOrlando Steel Enterprises, INC | Summerfield | FL | — | ◇ UNVERIFIED |
| OMOrleans Marble INC | Harahan | LA | — | ◇ UNVERIFIED |
| OFOryo Farms, Inc DBA Yoder's Portable Buildings | Mize | MS | — | ◇ UNVERIFIED |
