The List
There are 490 6 letter words with O as the first letter. The highest scoring is OZZIES at 24 points in Scrabble. 332 carry three or more vowels, which makes them useful for dumping a vowel-clogged rack.
OAFISHOAKERSOAKIEROAKIESOAKUMSOARAGEOARIEROARINGOATERSOATIEROBANGSOBDUREOBEAHSOBECHEOBEISMOBELIAOBELUSOBENTOOBESEROBEYEDOBEYEROBIINGOBIISMOBITALOBITEROBJECTOBJETSOBJUREOBLASTOBLATEOBLIGEOBLONGOBOISTOBOLESOBOLUSOBSESSOBSIGNOBTAINOBTECTOBTENDOBTESTOBTUNDOBTUSEOBVERTOCCAMSOCCAMYOCCIESOCCULTOCCUPYOCCURSOCEANSOCELLIOCELOTOCHERSOCHERYOCHONEOCHREAOCHREDOCHRESOCHREYOCICATOCKERSOCREAEOCTADSOCTALSOCTANEOCTANSOCTANTOCTAVEOCTAVOOCTETSOCTETTOCTOPIOCTROIOCTUOROCTYLSOCULAROCULUSODDESTODDISHODDITYODEONSODEUMSODIOUSODISMSODISTSODIUMSODOREDODOURSODYLESOECISTOEDEMAOEUVREOFFALSOFFCUTOFFENDOFFERSOFFICEOFFIESOFFINGOFFISHOFFKEYOFFPUTOFFSETOFLAGSOFTESTOGAMICOGDOADOGGINSOGHAMSOGIVALOGIVESOGLERSOGLINGOGRESSOGRISHOGRISMOHMAGEOIDIUMOIKISTOILCANOILCUPOILERSOILERYOILGASOILIEROILILYOILINGOILLETOILMANOILMENOILNUTOILWAYOINKEDOINTEDOJIMESOKAPISOKAYEDOLDENSOLDESTOLDIESOLDISHOLEATEOLEFINOLEINEOLEINSOLEUMSOLFACTOLINGOOLIVEROLIVESOLIVETOLLAMHOLLAVSOLLERSOLLIESOMASALOMASUMOMBERSOMBRESOMEGASOMELETOMENEDOMENTAOMERTAOMIGODOMLAHSOMNIFYOMNIUMOMRAHSONAGERONAGRIONBEATONCERSONCOMEONCOSTONDINEONDINGONEYERONEYREONFALLONFLOWONIONSONIONYONIRICONIUMSONLAYSONLINEONLOADONNINGONRUSHONSETSONSIDEONUSESONWARDONYCHAONYXESOOBITSOOCYSTOOCYTEOODLESOOFIEROOGAMYOOGENYOOHINGOOIDALOOLITEOOLITHOOLOGYOOLONGOOMIACOOMIAKOOMPAHOOMPHSOOPINGOORALIOORIALOORIEROOSIEROOTIDSOOZIEROOZILYOOZINGOPALEDOPAQUEOPCODEOPENEDOPENEROPENLYOPEPESOPERASOPERONOPHITEOPIATEOPINEDOPINESOPIOIDOPIUMSOPPOSEOPPUGNOPSINSOPTANTOPTERSOPTICSOPTIMAOPTIMEOPTINGOPTIONOPULUSOPUSESORACHEORACLEORALLYORANGEORANGSORANGYORANTSORARIAORATEDORATESORATORORBIERORBINGORBITAORBITSORBITYORCEINORCHATORCHELORCHIDORCHILORCHISORCINEORCINSORDAINORDEALORDERSORDUREOREADSOREIDEOREXINOREXISORFRAYORGANAORGANSORGEATORGIACORGIASORGIESORGONEORGUESORIBISORIELSORIENTORIFEXORIGANORIGINORIHOUORIOLEORISHAORISONORIXASORLONSORLOPSORMERSORMOLUORNATEORNERYOROGENOROIDEORPHANORPHICORPINEORPINSORRERYORRICEORTHOSORVALSORYXESOSCARSOSCINEOSCULAOSCULEOSETRAOSHACSOSIERSOSIERYOSMATEOSMICSOSMIUMOSMOLEOSMOLSOSMOSEOSMOUSOSMUNDOSPREYOSSEINOSSIFYOSTEALOSTENTOSTIALOSTIUMOSTLEROSTOMYOTALGYOTHERSOTIOSEOTITICOTITISOTTARSOTTAVAOTTERSOUBAASOUBITSOUCHEDOUCHESOUCHTSOUGHLYOUGHTSOUGLIEOUIJASOULDEROULONGOUNCESOUPHESOUPINGOURALIOURANGOURARIOUREBIOURIEROUSELSOUSTEDOUSTEROUTACTOUTADDOUTAGEOUTASKOUTATEOUTBAROUTBEGOUTBIDOUTBOXOUTBUYOUTBYEOUTCRYOUTDIDOUTEATOUTERSOUTFITOUTFLYOUTFOXOUTGASOUTGUNOUTHEROUTHITOUTINGOUTJETOUTJUTOUTLAWOUTLAYOUTLEDOUTLEROUTLETOUTLIEOUTMANOUTPUTOUTRANOUTREDOUTRIGOUTROSOUTROWOUTRUNOUTSATOUTSAWOUTSAYOUTSEEOUTSETOUTSINOUTSITOUTSUMOUTTOPOUTVIEOUTWAROUTWINOUTWITOUTWONOUVERTOUZELSOVALLYOVATEDOVATESOVATOROVENEDOVERBYOVERDOOVEREDOVERGOOVERLYOVIBOSOVINESOVISACOVISTSOVOIDSOVOLOSOVONICOVULAROVULESOWCHESOWELTYOWERBYOWLERSOWLERYOWLETSOWLIEROWLINGOWLISHOWNERSOWNINGOWRIEROXALICOXALISOXBOWSOXCARTOXEYESOXFORDOXGANGOXGATEOXHEADOXHIDEOXIDESOXIDICOXIMESOXLANDOXLIKEOXLIPSOXSLIPOXTAILOXTERSOXYGENOXYMELOYESESOYEZESOYSTEROZAENAOZALIDOZEKISOZONESOZONICOZZIES