ABSTRACT. Thirty Hereford steers were finished either on pasture (n = 10) or concentrate (n = 20) to determine dietary and antioxidant treatment effects on carcass characteristics, fatty acid composition, and quality of Uruguayan beef. Half of the steers finished on concentrate were supplemented with 1000 I.U. vitamin E head-1 day-1 for 100 days. Postmortem vitamin C was added to ground beef (0.05% v/w) displayed for 8 days at 2 °C. Carcasses from steers finished on concentrate had greater (P 0.05) between pasture- and concentrate-fed animals. However, beef from pasture-fed cattle had lower (P 0.05) TBARS values, which were lower (P 0.05) reduce lipid oxidation. Vitamin E supplementation of concentrate-fed cattle had no effect (P > 0.05) on color stability of ground beef or steaks. The a* (redness) and b* (yellowness) values were higher (P