Prescribed burning elevated the concentration of protein and in vitro digestible organic matter (IVDOM) in winter diets of mountain sheep (Ovis canadensis) and mule deer (Odocoileus hemionus) feeding in grassland and mountain shrub communities. We observed no effect of burning on ungulate nutrition during spring. In both communities, the magnitude of treatment effects tended to depend on the month we observed diets. Effects of burning on diet crude protein persisted for 2 years in both communities. Treatment effects on diet IVDOM lasted for 2 years in mountain shrub, but were absent during the 2nd year in grassland. Effects of fire on diet quality resulted from changes in ungulate diet selection rather than improvements in the quality of individual forages. Differences in the amount of green grass in ungulate diets accounted for much of the enhancement in diet quality we observed. We conclude that prescribed fire can improve winter habitats for mule deer and mountain sheep.