| Opto Circuits (India) Ltd (OPTOCIRCUI) NSE - National Stock Exchange of India | |
| Orissa Minerals Development Company Ltd (ORISSAMINE) NSE - National Stock Exchange of India | |
| Ocular Therapeutix Inc (OCUL) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| Oshkosh Corp (OSK) NYSE - The New York Stock Exchange | |
| Ollies Bargain Outlet Holdings Inc (OLLI) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| Omnicom Group Inc. (OMC) NYSE - The New York Stock Exchange | |
| OpGen Inc (OPGN) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| On Deck Capital Inc (ONDK) NYSE - The New York Stock Exchange | |
| OWC Pharmaceutical Research Corp (OWCP) OTCMKTS - OTC Markets | |
| Omaxe Ltd (OMAXE) NSE - National Stock Exchange of India | |
| Omkar Speciality Chemicals Ltd (OMKARCHEM) NSE - National Stock Exchange of India | |
| Ocean Power Technologies Inc (OPTT) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| Old Dominion Freight Line (ODFL) NASDAQ - National Association of Securities Dealers Automated Quotations | |
| ONEOK, Inc. (OKE) NYSE - The New York Stock Exchange | |
| Oil India Limited (OIL) BSE - Bombay Stock Exchange | |