A process for converting lower alcohols and oxygenates thereof either to gasoline-grade hydrocarbons or to olefins is improved by providing a reactor vessel having substantially no freeboard or a relatively short freeboard. The elimination or substantial elimination of the freeboard in the reactor minimizes contact time of the higher alkane and alkene hydrocarbons and aromatics-containing catalyst with the feed, thereby preventing the formation of additional higher hydrocarbons and aromatics, including durene. The catalyst is separated from the gaseous reaction products in a separate stripper/separator vessel by solids-gas separation means which return the catalyst to a fluidized bed in the downstream section of the stripper/separator vessel. The paraffins, olefins, naphthenes and aromatics are stripped from the catalyst in the fluidized bed of the stripper/separator vessel.