The List
There are 156 4 letter words with O as the first letter. The highest scoring is OYEZ at 16 points in Scrabble. 14 carry three or more vowels, which makes them useful for dumping a vowel-clogged rack.
OAFSOAKSOAKYOARSOARYOASTOATHOATSOATYOBASOBESOBEYOBIAOBISOBITOBOEOBOLOBOSOCASOCCYOCHEOCTAODAHODALODASODDSODEAODESODICODORODSOODYLOFAYOFFSOFFYOGAMOGEEOGLEOGREOHEDOHIAOHMSOIKSOILSOILYOINKOINTOKASOKAYOKEHOKESOKRAOKTAOLDEOLDSOLDYOLEAOLEOOLESOLIDOLIOOLLAOLMSOLPEOMBUOMENOMEROMITOMOVONCEONERONESONIEONLYONOSONSTONTOONUSONYXOOFSOOFYOOHSOOMSOONSOONTOOPSOOSEOOSYOOTSOOZEOOZYOPAHOPALOPEDOPENOPESOPPOOPTSOPUSORADORALORBSORBYORCAORCSORDOORDSORESORFEORFSORLEORRAORTSORYXORZOOSAROSESOSSAOTICOTTOOUCHOUDSOUKSOULDOULKOUMAOUPAOUPHOUPSOURNOURSOUSTOUTSOUZOOVALOVELOVENOVEROVUMOWEDOWEROWESOWLSOWLYOWNSOWREOWSEOWTSOXENOXEROXESOXIDOXIMOYEROYESOYEZ