| O | Realty Income Corp. | OLO | PowerShares DB Crude Oil Long | ORCH | Orchid Cellmark Inc. |
| OABC | OmniAmerican Bancorp Inc | OLP | One Liberty Properties Inc. | ORCL | Oracle Corp. |
| OAS | Oasis Petroleum Inc | OMAB | Grupo Aeroportuario del Centro Nort SAB | ORCT | Orckit Communications Ltd. |
| OB | OneBeacon Insurance Group | OMC | Omnicom Group Inc. | OREX | Orexigen Therapeutics, Inc. |
| OBAF | OBA Financial Services Inc | OMCL | Omnicell Inc. | ORGN | ORIGEN FINANCIAL INC |
| OBAS | Optibase Ltd. | OME | Omega Protein Corp. | ORH | Odyssey Re Holdings Corp. |
| OBCI | Ocean Bio Chemical | OMER | Omeros Corp | ORI | Old Republic International Corp. |
| OC | Owens Corning | OMEX | Odyssey Marine Exploration Inc. | ORIT | Oritani Financial Corp. |
| OCCF | Optical Cable Corp. | OMG | OM Group Inc. | ORLY | O'Reilly Automotive Inc. |
| OCFC | OceanFirst Financial Corp. | OMI | Owens & Minor Inc. | ORN | Orion Marine Group, Inc |
| OCLR | Oclaro, Inc. | OMN | OMNOVA Solutions Inc. | ORNG | Orange 21 Inc. |
| OCLS | Oculus Innovative Sciences, Inc. | OMNI | OMNI Energy Services Corp. | ORRF | Orrstown Financial Services Inc. |
| OCN | Ocwen Financial Corp. | OMPI | Obagi Medical Products, Inc. | ORS | Orsus Xelent Technologies Inc. |
| OCNF | OceanFreight, Inc. | OMTR | Omniture Inc. | ORXE | Ore Pharmaceuticals Inc. |
| OCNFD | Oceanfreight | OMX | OfficeMax Inc. | OSBC | Old Second Bancorp Inc. |
| OCNW | Occam Networks Inc. | ONAV | Omega Navigation Enterprises, Inc. | OSBCP | OLD SECOND CAP TR I |
| OCR | Omnicare Inc. | ONB | Old National Bancorp. | OSBK | Osage Bancshares Inc |
| OCZ | Ocz Technology | ONCY | ONCOLYTICS BIOTECH INC | OSCI | Oscient Pharmaceuticals Corp. |
| ODC | Oil-Dri Corp. of America | ONE | Higher One Holdings Inc | OSG | Overseas Shipholding Group Inc. |
| ODFL | Old Dominion Freight Line Inc. | ONEF | One Fund | OSHC | Ocean Shore Holding Co. |
| ODP | Office Depot, Inc. | ONEQ | FIDELITY NQ COMP IDX FD ETF | OSHCD | OCEAN SHORE HOLDING CO |
| ODSY | Odyssey Healthcare Inc. | ONFC | Oneida Financial Corp. | OSIP | OSI Pharmaceuticals Inc. |
| ODY | AB Svnsk Ekprtkrdt Aclrtd Rt Nts Lkd S&P | ONNN | ON Semiconductor Corp. | OSIR | Osiris Therapeutics, Inc. |
| OEF | ISHARES S&P 100 INDEX FD | ONP | Orient Paper Inc | OSIS | OSI Systems, Inc. |
| OEH | Orient-Express Hotels Ltd. | ONSM | Onstream Media Corp. | OSK | Oshkosh Corporation |
| OESX | Orion Energy Systems, Inc | ONT | On2 Technologies Inc. | OSM | SLM CORPORATION |
| OFC | Corporate Office Properties Trust Inc. | ONTY | Oncothyreon Inc | OSP | OSG America L.P. |
| OFG | Oriental Financial Group Inc. | ONVI | Onvia Inc. | OSTE | Osteotech Inc. |
| OFI | Overhill Farms Inc. | ONXX | Onyx Pharmaceuticals Inc. | OSTK | Overstock.com Inc. |
| OFIX | Orthofix International NV | OOK | OOK ETF | OSUR | OraSure Technologies Inc. |
| OFLX | OmegaFlex, Inc. | OOO | Stream Global Services, Inc. | OTE | Hellenic Telecommunications Organization SA |
| OGE | OGE Energy Corp. | OPEN | OpenTable, Inc. | OTEX | Open Text Corp. |
| OGXI | OncoGenex Pharmaceuticals, Inc. | OPHC | OptimumBank Holdings Inc. | OTIV | On Track Innovations Ltd. |
| OHB | Orleans Homebuilders Inc. | OPK | Opko Health, Inc. | OTIX | Otix Global, Inc. |
| OHI | Omega Healthcare Investors Inc. | OPLK | Oplink Communications Inc. | OTP | Claymore Ocean Tomo Patent ETF |
| OI | Owens-Illinois, Inc. | OPMR | Optimal Group Inc. | OTR | Claymore Ocean Tomo Growth Index |
| OIA | MSDW Muni Income Opportunity | OPMRD | Optimal Group | OTT | Otelco Inc. |
| OIB | MSDW Muni Income Opportunity II | OPNT | OPNET Technologies Inc. | OTTR | Otter Tail Co |
| OIC | MSDW Muni Income Opportunity III | OPOF | Old Point Financial Corporation | OUTD | Outdoor Channel Holdings, Inc. |
| OICO | OPTC | Optelecom-NKF Inc. | OVBC | Ohio Valley Banc Corp. | |
| OIH | OIL SERVICE HOLDERS TR 2041 | OPTR | Optimer Pharmaceuticals, Inc. | OVLY | Oak Valley Bancorp |
| OII | Oceaneering Intl Inc | OPTT | Ocean Power Technologies, Inc | OVRL | Overland Storage Inc. |
| OIIM | O2Micro International Ltd. | OPTV | OpenTV Corp. | OVRLD | Overland Storage |
| OIL | iPath S&P GSCI Crude Oil Tot Ret Idx ETN | OPWV | Openwave Systems Inc. | OVTI | OmniVision Technologies Inc. |
| OIS | Oil States International Inc. | OPXA | Opexa Therapeutics, Inc. | OWW | Orbitz Worldwide, Inc. |
| OKE | ONEOK Inc. | OPXT | Opnext, Inc. | OXGN | Oxigene Inc. |
| OKS | ONEOK Partners, L.P. | OPY | Oppenheimer Holdings Inc. | OXM | Oxford Industries Inc. |
| OKSB | Southwest Bancorp Inc (OK) | ORA | Ormat Technologies Inc. | OXPS | optionsXpress Holdings, Inc. |
| OKSBP | Southwest Bancorp Inc | ORB | Orbital Sciences Corp. | OXY | Occidental Petroleum Corporation |
| OLA | Old Mutual/Claymore Long-Short Fund | ORBC | ORBCOMM, Inc. | OYOG | Oyo Geospace Corp |
| OLBK | Old Line Bancshares Inc. | ORBK | Orbotech Ltd. | OZM | Och-Ziff Capital Management Group LLC |
| OLCB | Ohio Legacy Corp. | ORBT | Orbit International Corp. | OZRK | Bank of the Ozarks, Inc. |
| OLE | 9.25% Callable STRIDES Lnkd to Oracle | ORCC | Online Resources Corp. | ||
| OLN | Olin Corp. | ORCD | The Orchard Enterprises Inc. |
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