Bluebunch wheatgrass (Pseudoregneria spicata [Pursh] A. Love) is a major forage species for mountain sheep (Ovis canadensis) in central Idaho. Observed condition of this forage species is high, prompting an investigation of herbivory levels and subsequently nutrient content and biomass of this species. Mean amounts of tissue removed from wheatgrass plants on a slope frequently used by mountain sheep ranged from 5.3% to 26.8% from 1992–1996. Nitrogen levels ranged from 0.7–1.4% from 1998–2007 in plants collected in late June after seed-set. Higher levels of N occurred in growth following wildfire burns. Above-ground growth of bluebunch wheatgrass ranged from 11.3 to 102.1 gm/m² and was highly correlated with spring precipitation. While herbivory on this major forage species was low to moderate, nitrogen levels may vary enough to affect mountain sheep population trends without appreciably affecting productivity of their major forage species.