| Reg No. | Company Name | WEEE | Battery | Trading As Name | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 |
|---|---|---|---|---|---|---|---|---|---|---|
| 01361WB | O'Callaghan Leisure Ltd | YES | YES | NO | NO | NO | NO | Reg-Pending | Reg-Pending | |
| 00900W | O'Doherty Agencies | YES | NO | YES | YES | YES | YES | YES | YES | |
| 00849W | O'Donovan Engineering Company Ltd | YES | NO | YES | YES | YES | YES | YES | YES | |
| 01427W | O'Flynn Medical Ltd | YES | NO | N/A | N/A | N/A | N/A | YES | YES | |
| 00231W | O'Keeffes of KIlkenny Ltd | YES | NO | YES | YES | YES | YES | YES | YES | |
| 00093WB | O'Neill's Electrical Ltd | YES | NO | YES | YES | YES | WEEE YES | Reg-Pending | Reg-Pending | |
| 00511WB | OCE-Ireland Ltd | YES | NO | YES | YES | YES | BATT Reg-Pending | Reg-Pending | Reg-Pending | |
| 00292WB | Office Depot (Ireland) Ltd | YES | YES | Office Depot | YES | YES | YES | YES | YES | YES |
| 01331WB | Ogalas Ltd | YES | YES | Homestore & More | N/A | N/A | N/A | N/A | YES | YES |
| 00236WB | OKI Systems (Ireland) Ltd | YES | YES | YES | YES | YES | YES | YES | YES | |
| 00927WB | Oltech (Systems) Ltd | YES | NO | YES | YES | YES | YES | WEEE YES | Reg-Pending | |
| 01602WB | Online Retail Solutions Ltd | YES | YES | NO | NO | NO | NO | NO | Reg-Pending | |
| 00324W | Open G I Ltd | YES | NO | YES | YES | YES | YES | YES | YES | |
| 00918WB | Optical Sciences (Ireland) Ltd | YES | YES | YES | YES | YES | YES | YES | YES | |
| 00721W | Option Wireless Ltd | YES | NO | YES | YES | YES | YES | YES | YES | |
| 01585WB | Oracle EMEA Ltd | YES | YES | Oracle Corporation | N/A | N/A | N/A | N/A | N/A | Reg-Pending |
| 01582WB | Orega Systems Ltd | YES | YES | YES | YES | YES | YES | YES | YES | |
| 00083WB | Origo Distribution Ltd | YES | YES | Origo | YES | YES | YES | YES | YES | YES |
| 00239W | Osmosis Ireland Ltd | YES | NO | YES | YES | YES | YES | YES | YES | |
| 00211WB | Osram Ltd | YES | YES | Osram | N/A | YES | YES | YES | YES | YES |
| 00808W | Outdoor Garden Products Ltd | YES | NO | N/A | YES | YES | YES | YES | YES | |
| 00460WB | Oxendale & Co. Ltd | YES | YES | YES | YES | YES | YES | YES | YES | |
| 00600WB | Oxygen-Care Ltd | YES | YES | YES | YES | YES | YES | YES | YES |