This study was conducted to examine the effects of Red clay(Hwangto) as feed additives with 26 Hanwoo steers at two regions for 540 days from six to 24 months of age on feed efficiency, meat quantity and meat quality. Feeding trial 1 was conducted with two treatment groups by five heads/treatment which were T1(Control) and T2(Control+ad libitum Hwangto) at National Livestock Research Institute. Feeding trial 2 was conducted with four treatment groups by four heads/treatment which were T1(Control), T2(Control+2% Hwangto), T3(Control+5% Hwangto) and T4(Control+ad libitum Hwangto) at a private Hanwoo breeding farm. In feeding trial 1, average daily gains by growing, fattening, finishing and over-all periods were 0.572, 0.866, 0.869 and 0.769kg in T1, and 0.537, 0.904, 0.857 and 0.766kg in T2, respectively. Average daily gain for growing and finishing period was high in T1 but in T2 for fattening period, which were not statistically significant. Also concentrates and TDN intakes per kg gains were not statistically significant by treatments. In carcass characteristic, dressed carcass and red meat percentage were high in T1 but in T2 for retailed cut percentage without significant difference. The yield index and shear force was 69 and 70, 4.4 and 6.1 kg/$cm^2$ in T1 and T2, respectively. In palatability traits, the panel test scores of juiciness, tenderness and flavor were 4.08 and 4.64, 3.42 and 3.96, 4.58 and 4.80 in T1 and T2, respectively. which showed a tendency to improvement in Hwangto feeding groups. In feeding trial 2, the range of average daily gains were 0.656(T6) to 0.772(T3), 0.937(T6) to 1.009(T5), 0.592(T3) to 0.675kg(T6) in growing, fattening and finishing period, respectively. Although it was high in T3, T5 and T6 at growing, fattening and finishing period, respectively, it was not significantly different by treatments. The ranges of concentrates and TDN intakes per kg gains were 8.71 to 9.50(average 9.05) and 7.52 to 7.64kg(average 7.55kg), they all were lower in Hwangto feeding groups than in control about 4.5 to 8.3% and 1.2 to 1.6%, respectively. In carcass characteristics, back-fat thickness, loin eye muscle area and yield index were not difference by treatments, but marbling scores were high in T5 and T6 than in percent. Summarizing above results, it may be concluded that the use of unprocessed Hwangto as feed additives for growing-fattening steers seems to improve meat quality but not red meat quantity and feed efficiency, and may be required to feed ad libitum during the finishing period.