Technical Abstract: Extending the grazing season into the fall and winter increases the sustainability of livestock production by reducing winter feed costs. However, without exception, stockpiled range grasses do not meet nutritional requirements for ruminant livestock. This study compared fall/winter grazing of traditional, grass-dominated rangelands to rangelands improved by seeding forage kochia (Kochia prostrata). Carrying capacity, forage nutritive value, and cattle body condition were determined in 2007 and 2008 using landscape scale, on-farm trials. The study was conducted from late October to early January at two locations near Tooele, Utah. Forage yield on the treated rangeland was 2309 lbs per acre, which was 6 times greater (P = 0.001) than the untreated rangeland. Differences in forage production resulted in carrying capacities of 1.38 and 0.24 AUM per acre for the treated and untreated rangelands, respectively. Grass production was similar (P = 0.564) between the two rangelands, thus forage kochia, which made up 74% of the biomass was primarily responsible for the increased production. Forage kochia had higher (P = 0.033) crude protein (11.7%) than the stockpiled grass (3.1%) and met the minimum of 7.0% recommended to maintain rumen function in late-gestation cattle. Although, both groups of cattle improved in body condition, there was a trend (P = 0.152) for cows in the treated rangeland to improve more inbody condition score (+0.7) than the cows in the untreated rangeland (+0.4). This study indicates that forage kochia can improve sustainability of livestock production in the western U.S. by increasing rangeland carrying capacity and forage nutritive value.