Cattle production on desert grassland ranges in southern New Mexico has been low, although limited research shows diet nutritional quality of cattle is adequate to meet production needs during most seasons. Forage intake data are lacking for cattle on desert grassland ranges. Five esophageal-fistulated steers were used to evaluate diet quality and botanical composition on desert grassland range in southern New Mexico. Another 6 steers were used to collect feces to determine intake. Cattle changed their diet with seasonal advance to maximize diet quality. Crude protein concentrations of cattle diets were well above those needed for lactation and daily gain during spring and summer. Diet samples were high in neutral detergent fiber (66-81%), suggesting low energy in the forage. Low forage intake was the main nutritional constraint Identified. Even during the summer growing season, organic matter intake never exceeded 1.5% of body weight. We speculate low intakes may have resulted from high summer temperatures that reduced grazing time. During the late fall and winter, low forage quality appears to explain suppressed Intake. Protein supplementation in late fall and winter, and energy supplementation in spring, should be advantageous. We caution that data on diet quality without information on forage intake may poorly describe nutritional status of range cattle.