Uruguayan meat production systems are based mainly on grazing pastures. More intensive systems have been growing by adding concentrate to grazing animals to improve performance and beef carcass and meat quality. Thirty two Hereford steers of 20 months of age, were randomly assigned to 4 treatments as a result of combining 2 levels of forage allowance (LFA:2% and 4% of live weight LW) and supplementation (S:0.8 and 1.6 % of ground sorghum), where:T1 = 4 % LFA + 0 % S; T2 = 2 % LFA + 0 % S; T3 = 2 % LFA + 0.8 % S and T4 = 2 % LFA + 1.6 % S. Steers from T1 and T4 produced heavier carcasses (HCW) and higher back fat thickness (BFT). When HCW is adjusted by final live weight (FLW) the differences disappeared, showing that differences were due basically for different final weight. Same tendency was observed for the weight of the most valuable meat cuts. Treatments did no affect (P>0.05) ultimate pH, intramuscular fat, meat color at 48 hours after slaughter, tenderness of meat aged for 7 and 20 days. No treatment differences on PUFA concentration and PUFA/SFA and n6/n3 ratio were found. However, meat of T4 animals presented the higher concentration of MUFA, particularly oleic fatty acid. Meat of treatments based only on pasture (T1 and T2) presented the higher concentration of linolenic and stearic fatty acids. Meat produced on grass-fed or combined with low supplement levels, could promote human health.