An algorithm for estimating supportable densities of herbivores consuming diets at different levels of nutritional quality is given. This procedure is used to predict carrying capacity of burned and unburned mountain shrub habitat for mule deer (Odocoileus hemionus) and mountain sheep (Ovis canadensis). The resulting predictions are compared with those of traditional range supply/animal demand models. Unburned areas had higher carrying capacities for animals consuming low quality diets, but burned areas could support more animals on a high plane of nutrition. Traditional procedures for estimating carrying capacity failed to detect these interactions between carrying capacity and animal nutritional status. Reliable evaluation of relationships between range food supplies and animal food requirements must treat forage amount and quality as integrated rather than distinct features of habitat.