Growth and individual cumulative feed intakes (cumFI) of 15 Brahman, 12 Bonsmara and 14 Drakensberger bulls, randomly acquired from various herds, were recorded in a 140-day postweaning feedlot trial. Of the linear and quadratic regressions fitted to the data of each animal, the quadratic expression showed the best fit. Average daily gain (ADG), average daily feed intake (ADFI) and average feed conversion efficiency (FCE) were obtained from differentials of the resultant equations. Corrected, pooled means of performance traits for the Brahman, Bonsmara and Drakensberger were (P < 0,05) initial mass: 211a, 230a, and 236a; final mass: 352a, 442b, and 403b; cumFI: 876a, 1164b, and 1243b,; ADG: 1,01a, 1,51b, and 1,20a; ADFI: 6,26a, 8,31b, and 8,88b; FCE: 6,36ab, 5,57a, and 7,42b. The conclusion is that a substantial genetic basis exists for variation in ADFI, gain and FCE for bulls on postweaning performance tests.