A multiphase porous media model was developed to predict moisture transport during intensive microwave heating of biomaterials. Internal pressure gradients arise from internal heating and vaporization and significantly enhance the transport. Even a moderate internal pressure gradient in a low moisture material can cause more moisture to move to the surface than can be removed from the surface, leading to a soggy surface. A strong internal pressure gradient in a high moisture material can fully saturate the surface, leading to a very high moisture loss by liquid outflow at the surface. Addition of hot air and/or infrared heating of the surface to increase evaporation is suggested as a way to reduce surface moisture build-up.