Effects of supplementing cattle consuming forage with rice bran and(or) corn on feed intake, digestibility, and live weight gain were determined. Holstein steer calves (176 +/- 4.3 kg average trial BW), in two simultaneous 4 x 4 Latin squares, had ad libitum access to bermudagrass or ryegrass-wheat hay without supplementation (Control) or with (DM basis) .5% of BW of ground corn (C), .64% of BW of rice bran (R), or .25% of BW of corn plus .32% of BW of rice bran (CR). Total OM intake with bermudagrass diets was less for R than for C, but values for R and C were not different with ryegrass-wheat (forage source x supplement type interaction; P < .05). An interaction (P < .06) between supplement type and forage source also occurred in digestible OM intake (3.33, 3.66, 2.93, 3.37, 3.77, 4.04, 3.73, and 3.94 kg/d for Control, C, R, and CR with bermudagrass and ryegrass-wheat, respectively). Mature beef cows (504 +/- 25.5 kg BW), in a 6 x 6 Latin square, were limit-fed ryegrass-wheat and alfalfa hay (3:1; air-dry basis) without supplementation (Control) or with (DM basis) .2 or .4% of BW of ground corn (L-C and H-C), .26 or .52% of BW of rice bran (L-R and H-R), or .2% of BW of corn plus .26% of BW of rice bran (H-CR). Duodenal flows of total (125, 122, 123, 137, 136, and 129 g/d) and microbial N (63.3, 64.7, 64.8, 70.3, 73.1, and 65.1 g/d for Control, L-C, H-C, H-R, and H-CR, respectively) were greater (P < .05 and .06, respectively) for rice bran than for corn supplements. Crossbred beef steers (96; 235 +/- 3.2 kg initial BW) of two frame sizes, with half treated with an estrogenic growth promotant, grazed fescue-clover and received Control, L-C, H-C, L-R, H-R, and H-CR supplements for 84 d. Supplement amounts were 50% greater relative to BW than in the preceding experiment. Overall ADG was increased (P < .05) by supplementation and was affected (P < .05) by a supplement type x level interaction (.71, .76, .97, .85, .76, and .94 kg/d for Control, L-C, H-C, L-R, H-R, and H-CR, respectively). Neither frame size nor growth implant modified effects of supplement treatments on ADG.