The List
There are 269 7 letter words with O as the last letter. The highest scoring is PALAZZO at 27 points in Scrabble. 259 carry three or more vowels, which makes them useful for dumping a vowel-clogged rack.
AGITATOAILANTOAKIRAHOALBERGOALFREDOALLEGROAMORINOAMOROSOANIMATOANNATTOAPAREJOAPPALTOARBORIOARNATTOARNOTTOARRIEROASINICOATISHOOAVOCADOAZULEJOBACALAOBAMBINOBANDITOBAROCCOBARRICOBATTEROBATTUTOBEEFALOBIZARROBONIATOBOTARGOBRACCIOBRACEROBRASEROBRAVADOBRONCHOBUCARDOBUDGEROBUFFALOBUGABOOBUMMALOBURRITOBUSHIDOCABILDOCALALOOCALANDOCALYPSOCANTICOCARABAOCASSINOCATTALOCAVETTOCEMBALOCENTAVOCENTIMOCERRADOCHAMISOCHANOYOCHEERIOCHICANOCHORIZOCLARINOCOMMODOCONCEDOCOQUITOCORANTOCORNUTOCRIOLLOCRUSADOCRUZADOCURACAOCYMBALODIABOLODINITROEIGHTVOELECTROEMBARGOESPARTOETAERIOFAGOTTOFARRAGOFERRUGOFINNSKOFORZATOFUMETTOFURIOSOGAMBADOGESTAPOGIOCOSOGRADINOGUANACOHAPKIDOHIDALGOHISTRIOHORNITOHUANACOIMPASTOINFERNOKARENGOKERCHOOLENTIGOLLANEROLUMBAGOMADRONOMAESTROMAFIOSOMAGNETOMALICHOMANGEAOMARCATOMARENGOMARRANOMEMENTOMENDIGOMESTESOMESTINOMESTIZOMISTICOMOCKADOMODELLOMOMENTOMONTEROMORELLOMORENDOMORISCOMOROCCOMULATTONATHEMONAVARHONELUMBONITROSONONETTONONHERONONZERONORTENOOKIMONOOLOROSOOREGANOOUTECHOPACHUCOPAESANOPAISANOPAKAPOOPALAZZOPAMPEROPAPILIOPASSADOPATRICOPEDREROPEEKABOPEKEPOOPENTITOPERSICOPIANINOPICACHOPICCOLOPIFFEROPIMENTOPINTADOPINTANOPLACEBOPLENIPOPOBLANOPOINADOPOMPANOPOMPELOPORCINOPORRIGOPORTICOPOTOROOPRIMEROPRIVADOPROVISOPROXIMOPRURIGOPUMMELOQUOMODORABBITOREJONEORELIEVORELLENOREVERSORIDOTTORILIEVORIPIENORISOTTOROGALLORONDINOROSOLIORUBABOOSAGUAROSAHUAROSALTATOSAMSHOOSANTEROSAPSAGOSCALADOSCHERZOSCIOLTOSCREAMOSECONDOSEMIPROSENECIOSENTIMOSERPIGOSERRANOSFUMATOSHAKUDOSHAMPOOSIROCCOSKIDDOOSMOKEHOSOLDADOSOPRANOSORDINOSQUACCOSTELLIOSTRETTOSUBECHOSUBZEROSUPREMOSYNCHROTALLYHOTAMARAOTANGELOTARTUFOTENTIGOTESTUDOTHEORBOTHERETOTIMPANOTOBACCOTOMBOLOTONDINOTORNADOTORPEDOTOSTADOTOURACOTREMOLOTROMINOTWIGLOOTYMPANOUNDERDOUNDERGOUNMACHOUPTEMPOVAQUEROVERISMOVERTIGOVIBRATOVILIACOVILIAGOVIRANDOVOLCANOVOLPINOWENDIGOWHERESOWHERETOWINDIGOZAMARROZANJEROZAPATEOZEBRANOZEMSTVOZINGANOZINGAROZOCCOLOZORILLOZUFFOLO