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Early weaning of calves can improve reproduction of beef cows, and would be of no detriment to calf growth if the diet is adequate. Digestible energy intake could be limiting, however, when calves are weaned on forage. Performance of calves weaned at 70 days (early weaning) and 172 days (normally weaning) of age were compared. Calves from 2 locations in Argentina, Anguil, and Chacharramendi, were distributed in 14 groups and half were weaned. Early-weaned calves were pen fed a 50% concentrate-50% alfalfa hay diet for 12 days, followed by grazing on alfalfa for 150 days. During the first 90 days on pasture, early-weaned calves were group supplemented (1.2 % body weight (BW, DM basis). Calves from Anguil did not differ (P = 0.068) in average daily gain (ADG). In contrast, early-weaned calves from Chacharramendi gained faster than normally-weaned calves (P 0.01). In a second experiment, 108 calves were classified into 3 age groups on day 0 of trial (AGE1 = 109 +/- 2.2 days of age, AGE2 = 91 +/- 1.6 days of age and AGE3 = 75 +/- 3.8 days of age). Two thirds of the calves were weaned (early-weaned calves) the same day and the remaining third was returned to their dams (normally-weaned calves). Two feeding treatments were imposed on the early-weaned calves: S15 = supplement during the first 15 days on pasture (1% body weight, DM basis), and S45 = supplement during the first 45 days. Early-weaned calves grazed on an alfalfa pasture for 136 days. Calves from the normally-weaned group remained with their mothers until weaning onto pasture on day 87 of the study. Normally-weaned calves were the heaviest (P < 0.05) at the end of trial. Differences in body weight between early weaning ages increased as the supplementation period decreased. Calves that were weaned at 75 days of age and fed supplement for only 15 days had the lowest (P < 0.05) overall ADG and final body weight. Overall results suggested that early weaning favors reproduction of thin cows, and early-weaned calves can be placed on good-quality pasture with no detriment of growth if energy supplement is provided. The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information. Migrated from OJS platform August 2020