The aim of this study was to evaluate the effects of native grass on growth performance, carcass characteristics, and meat quality of Mongolian lambs fed Inner Mongolia native grass in three forms: grass, hay, and hay with concentrate (HC). Sixty Mongolian noncastrated male lambs, in good health and with the same age (6 mo) and similar body weights (mean, 28.63 ± 0.19 kg), were randomly divided into three treatments. There were four replicates in each treatment, with five lambs in one pen as a replicate. Compared with the HC group, the intake of the grass group was higher (P < 0.05) and that of the hay group was lower (P < 0.05). The hay group had a gain of -58.67 g d^-1, compared with 42.33 g d^-1 for the HC group and 80.00 g d^-1 for the grass group. The carcass weight, net meat mass, loin muscle area, and fat thickness (a measure of fat tissue thickness) were greater in the grass and HC groups than in the hay group (P < 0.05). Compared with the hay group, the protein and calcium contents, marbling score, and water loss rate were greater in the grass and HC groups (P < 0.05), whereas the fat, phosphorus, cholesterol contents, and b^* score were lower for the latter groups (P < 0.05). These results suggest that feeding of native grass hay with concentrate could improve the growth performance and meat quality of Mongolian lambs and achieve results similar to those observed in grass-fed lambs.