The objective of this study was to determine if pasture or grain diets affect oxidative/antioxidative status and the color stability of beef during retail display. Ten crossbreed steers were fed on pasture. Five of them were randomly assigned to remain on this diet, and the other five were finished on feedlot system (grain diet) during 110days until slaughter. Slices of Psoas major steaks were randomly distributed among retail display times (1, 3, 5, 7 and 9days). Lipid and protein oxidation were higher in Psoas major steaks from grain diet than in pasture diet (P<0.05). After 3days of display, lipid oxidation increased in meat from grain diet, whereas in meat from pasture diet the first evidence was after 7days (P<0.05). Protein oxidation was higher in meat from grain diet than in meat from pasture diet at day 9 of display (1.15±0.92 vs. 1.91±0.70μg/g, respectively; P<0.05). Antioxidant vitamins, α-tocopherol and β-carotene were higher at time=0 in pasture Psoas major steaks (P<0.05) and were differentially reduced throughout storage. While α-tocopherol decreased 41% and 57% for pasture and grain beef respectively (P<0.05), β-carotene levels remained practically unaffected in grain beef. After 7days of display "a" value was higher for Psoas major steaks from pasture diet (P<0.05). Besides, "L" parameter showed higher values for samples from grain diets but it was no affected by display time. No differences were observed between both treatments for "b" value, but a significant decrease (P<0.05) was observed along storage. Superoxide dismutase and catalase activity was stable throughout storage, while glutathione peroxidase activity decreased significantly (P<0.05). The results in this study demonstrated that the higher initial level and synergistic action (under light and air) of α-tocopherol and β-carotene found in pasture-finished animals improved the oxidative and color stability of beef, as showed by a better retention of redness at the end of retail display.