Twenty crossbred beef steers and twenty crossbred beef heifers were randomly allotted to two treatments to evaluate the effect of supplementation on animal performance in animals grazing cotton plant residues: (1) 10 steers and 10 heifers were allowed to graze ad libitum in an 8 ha cotton field after harvest, and (2) 10 steers and 10 heifers grazed in a similar field but received 1 kg day −1 of supplement. Water intake and mineral consumption were measured daily. Cotton plant residues were obtained from an adjacent 10 ha field by collecting 12 representative samples using a 1 m 2 frame, and separating leaves and cottonseeds for lab analysis. Dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose, lignin, silica, calcium, phosphorus and nitrogen ADF were determined. Supplementation did not affect the total weight gain of the steers or the heifers during the 30-day grazing period. The unsupplemented steers gained 0.500 kg day −1 , while the supplemented steers gained 0.466 kg day −1 . The supplemented and unsupplemented heifers gained 0.266 kg and 0.233 kg day −1 , respectively. Water intake did not differ between treatments, but mineral consumption was significantly greater for the unsupplemented calves. The total cotton residues in the soil accounted for about 2,100 kg ha −1 of DM. The economic analysis indicated an increased profitability when using steer calves without supplementation.