Extending grazing into the winter increases the sustainability of livestock production. However, stockpiled range grasses do not meet livestock nutritional requirements. This study compared winter grazing of grass-dominated (untreated) and forage kochia-dominated (Kochia prostrata) (treated) rangelands. Carrying capacity, forage nutritive value, and cattle body condition were determined during late October to early January using landscape-scale trials in Utah. Forage production on the treated rangeland (2,309 lbs/acre) was 6 times greater (P = 0.001) than the untreated rangeland, resulting in carrying capacities of 1.38 and 0.24 AUM/acre for the treated and untreated rangelands, respectively. Grass production was similar (P = 0.564) between the two rangelands, thus forage kochia was primarily responsible for the increased carrying capacity. 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 for gestating 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 in body 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 by increasing rangeland carrying capacity and forage nutritive value.