Fluidized bed reactors for steam methane reforming, with and without immersed membrane surfaces for withdrawal of hydrogen, are modeled with oxygen added in order to provide the endothermic heat required by the reforming reactions. Porous alumina, palladium and palladium-coated high-flux tubes are investigated as separation materials, the latter two being permselective. Hydrogen yield and permeate hydrogen molar flow are predicted to decrease with increasing oxygen flow, and to increase with temperature. When the steam-to-carbon ratio increases, permeate hydrogen yield decreases slightly, while the total hydrogen yield increases for all configurations. The flow of oxygen required to achieve autothermal conditions depends on such factors as the reactor temperature, steam-to-carbon ratio and preheating of the feed.