The List
There are 260 5 letter words with O as the first letter. The highest scoring is OZZIE at 23 points in Scrabble. 105 carry three or more vowels, which makes them useful for dumping a vowel-clogged rack.
OAKEDOAKENOAKEROAKUMOAREDOASESOASISOASTSOATENOATEROATHSOAVESOBANGOBEAHOBELIOBESEOBEYSOBIASOBIEDOBIITOBITSOBJETOBOESOBOLEOBOLIOBOLSOCCAMOCCUROCEANOCHEROCHESOCHREOCHRYOCKEROCREAOCTADOCTALOCTANOCTASOCTETOCTYLOCULIODAHSODALSODDERODDLYODEONODEUMODISMODISTODIUMODORSODOURODYLEODYLSOFAYSOFFALOFFEDOFFEROFFIEOFLAGOFTENOFTEROGAMSOGEEDOGEESOGGINOGHAMOGIVEOGLEDOGLEROGLESOGMICOGRESOHIASOHINGOHMICOHONEOIDIAOILEDOILEROINKSOINTSOJIMEOKAPIOKAYSOKEHSOKRASOKTASOLDENOLDEROLDIEOLEICOLEINOLENTOLEOSOLEUMOLIOSOLIVEOLLASOLLAVOLLEROLLIEOLOGYOLPAEOLPESOMASAOMBEROMBREOMBUSOMEGAOMENSOMERSOMITSOMLAHOMOVSOMRAHONCERONCESONCETONCUSONELYONERSONERYONIONONIUMONKUSONLAYONNEDONSETONTICOOBITOOHEDOOMPHOONTSOOPEDOORIEOOSESOOTIDOOZEDOOZESOPAHSOPALSOPENSOPEPEOPERAOPINEOPINGOPIUMOPPOSOPSINOPTEDOPTEROPTICORACHORACYORALSORANGORANTORATEORBEDORBITORCASORCINORDERORDOSOREADORFESORGANORGIAORGICORGUEORIBIORIELORIXAORLESORLONORLOPORMERORNISORPINORRISORTHOORVALORZOSOSCAROSHACOSIEROSMICOSMOLOSSIAOSTIAOTAKUOTARYOTHEROTTAROTTEROTTOSOUBITOUCHTOUENSOUGHTOUIJAOULKSOUMASOUNCEOUNDYOUPASOUPEDOUPHEOUPHSOURIEOUSELOUSTSOUTBYOUTDOOUTEDOUTEROUTGOOUTREOUTROOUZELOUZOSOVALSOVARYOVATEOVELSOVENSOVERSOVERTOVINEOVISTOVOIDOVOLIOVOLOOVULEOWCHEOWINGOWLEDOWLEROWLETOWNEDOWNEROWRESOWRIEOWSENOXBOWOXERSOXEYEOXIDEOXIDSOXIESOXIMEOXIMSOXLIPOXTEROYERSOZEKIOZONEOZZIE