* Businesses in Bold are Chamber Members
| Company | Address | Phone Number |
| O'Daniel Enterprise, LLC | 608-872-2519 | |
| Oak Street Laundromat | 204 West Oak | |
| Olsen's Mill, Inc. | 6250 Borden Road | 608-375-2800 |
| Oman Water Systems & Plumbing | 103 Superior Street | 608-375-5469 |
| Orthodox Byzantine Icons | 2750 Spring Valley Road | 608-375-5500 |
* Businesses in Bold are Chamber Members