| O'Connor Plumbing MD | Construction | 0 | — | C |
| O'Connor Plumbing and Heating, LLC NY | Construction | 0 | — | F |
| O'Connor Woods CA | Healthcare & Social Assistance | 0 | — | F |
| O'Connor Woods Housing Corp CA | Healthcare & Social Assistance | 0 | — | F |
| O'Connor's Irish Pub NE | — | 0 | — | — |
| O'Daniel Auto Group Inc IN | Retail Trade | 0 | — | A |
| O'Daniel Automotive Inc IN | Retail Trade | 0 | — | B |
| O'Day Equipment LLC MN | Wholesale Trade | 0 | — | A |
| O'Day Equipment LLC ND | Wholesale Trade | 0 | — | D |
| O'Day Equipment LLC Elk River MN | Wholesale Trade | 0 | — | A |
| O'Day Management LLC ND | Wholesale Trade | 0 | — | A |
| O'Day Tank & Steel ND | Manufacturing | 0 | — | A |
| O'Donal's Acquisition company, LLC ME | Agriculture & Forestry | 0 | — | F |
| O'Donal's Nursery ME | Agriculture & Forestry | 0 | — | F |
| O'Donnell Impact Windows & Storm Protection FL | Construction | 0 | — | F |
| O'Donnell Landscapes Inc FL | Construction | 0 | — | F |
| O'Donnell/Snider Construction, LLC TX | Construction | 0 | — | A |
| O'Dorisio Carpentry & Concrete, LLC VA | Construction | 0 | — | A |
| O'Dorisio Carpentry and Concrete LLC VA | Construction | 0 | — | C |
| O'Flaherty Law, P.C. IL | Professional & Technical Services | 1 | $75,000 | — |
| O'Gara Hess Eisenhardt Armoring Company, LLC OH | — | 0 | — | — |
| O'Gorman Brothers, Inc. NJ | Construction | 0 | — | F |
| O'Gorman Brothers, Inc. dba Bath Fitter NJ | Construction | 0 | — | F |
| O'Gorman Brothers, LLC dba Bath Fitter FL | Construction | 0 | — | F |
| O'Grady Paving, Inc. CA | Construction | 0 | — | F |
| O'Grady Peyton International GA | Administrative & Waste Services | 20 | $66,174 | — |
| O'Grady's Landscape & Lawn Care, Inc. VA | Administrative & Waste Services | 0 | — | A |
| O'Hair Shutters TX | Manufacturing | 0 | — | F |
| O'Halloran International IA | Wholesale Trade | 0 | — | A |
| O'Hara Corporation WA | Agriculture & Forestry | 0 | — | F |
| O'Hare Airport Transit System, Inc (OATS) IL | Transportation & Warehousing | 0 | — | A |
| O'Hare Engineering IL | Construction | 0 | — | A |
| O'HARE FOUNDRY CORPORATION MO | Manufacturing | 0 | — | F |
| O'Keefe Millwork WI | Manufacturing | 0 | — | F |
| O'Keefe Millwork.com WI | Manufacturing | 0 | — | A |
| O'keeffe's Inc CA | Manufacturing | 0 | — | A |
| O'Leary Asphalt Inc. MD | Construction | 0 | — | A |
| O'Malley Beverage of KS, Inc. KS | Transportation & Warehousing | 0 | — | A |
| O'Malley Construction Company IL | Construction | 0 | — | A |
| O'Malley Construction Inc MN | Construction | 0 | — | A |
| O'Malley Timber Products VA | Manufacturing | 0 | — | F |
| O'Malley Wood Products PA | Manufacturing | 0 | — | F |
| O'Mara Landscaping & Lawn Care Inc. NC | Administrative & Waste Services | 0 | — | F |
| O'Meara Wagner P.A. MN | Professional & Technical Services | 0 | — | A |
| O'Melveny & Myers LLP CA | Professional & Technical Services | 6 | $280,833 | — |
| O'Neal Brothers Insulation, LLC TX | Construction | 0 | — | A |
| O'Neal Construction, Inc. MI | Construction | 0 | — | A |
| O'NEAL EXCAVATING AND CONSTRUCTION INC IN | Construction | 0 | — | F |
| O'Neal FB&E AL | Transportation & Warehousing | 0 | — | A |
| O'Neal Golf Management LLC IN | Arts & Entertainment | 0 | — | A |
