Growth performance (n=158) and carcass characteristics of 5 Awassi (A), 5 Morkaraman (M) and 4 Tushin (T) lambs weaned at 2.5 months of age were evaluated. The lambs were fed a concentrate mixture and allowed to graze for 70 days. At the end of the 70-day grazing period, M lambs showed the highest daily weight gain and the amount of concentrate consumed per body weight gain. The effects of breed and sex of lamb on daily weight gain on pasture were significant (P<0.05) and highly significant (P<0.01), respectively. Male lambs were superior to female lambs with respect to daily weight gain. Slaughter traits and carcass characteristics of 14 male lambs representing three fat-tailed breeds were compared at the end of the grazing period of the year in which they were born. Hot carcass weight and hindshank weight of M lambs were heavier than those of A and T lambs. M had higher hot dressing percentage and larger M. longissimus dorsi (LD) area than those of A and T lambs. Most of the weights of wholesale cuts were significantly (P<0.05; P<0.01) affected by breed. It is recommended that either A, M and T male and female lambs weaned at 2.5 months of age in eastern Turkey should be fed with 450 g concentrate per head per day on pasture for 3 to 3.5 months of grazing season, or lambs should be supplemented with more than 450 g concentrate feed on pasture because native fat-tailed breeds supplemented with 450 g concentrate on pasture did not give carcasses with an adequate commercial weight in the 70-day fattening period.