| Old Republic International Corporation (ORI) NYSE - The New York Stock Exchange | |
| Orient Cement Ltd (ORIENTCEM) BSE - Bombay Stock Exchange | |
| Oricon Enterprises Ltd (ORICONENT) NSE - National Stock Exchange of India | |
| Office Depot Inc (ODP) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| OPTEC INTL INC (OPTI) OTCMKTS - OTC Markets | |
| On4 Communications Inc (ONCI) OTCMKTS - OTC Markets | |
| Opko Health Inc. (OPK) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| Organovo Holdings Inc (ONVO) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| Om Metals Infraprojects Ltd. (OMMETALS) BSE - Bombay Stock Exchange | |
| Orchid Pharma Ltd (ORCHIDPHAR) BSE - Bombay Stock Exchange | |
| Orient Abrasives Ltd. (ORIENTABRA) NSE - National Stock Exchange of India | |
| Olympic Steel, Inc. (ZEUS) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| O'Reilly Automotive Inc (ORLY) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| Orthofix International NV (OFIX) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| Otelco Inc (OTEL) NASDAQ - National Association of Securities Dealers Automated Quotations | |