This experiment was conducted to determine harvesting date and cultivar effect on the yield and quality of forage rape (Brassica napus Subsp. oleifera) in comparison with Cayuse oats (Avena sativa L.) at the Experimental Livestock Farm, Seoul National University, Suweon during 1983-1984. A split-plot design with three replicates was used with harvesting date as main plots and cultivar as subplots. Agronomic characteristics, forage yield and quality measurements were taken in the experiment. Ramon, Velox, Barsica and Viva cultivars were classified as an early growing rape according to the plant height and maturity. Mean dry matter yield of forage rape and oats harvested at the late date was significantly higher than that of those crops harvested at the early date. In 1983. the dry matter yield of Ramon was highest at the early harvest, but Velox and Ramon were highest at the late harvest. In 1984, Ramon gave the highest dry matter yield at the early harvest, but Velox and Viva showed the highest at the late harvest. Mean dry matter yield of rape cultivar was higher than that of oats at the both harvesting dates. The crude protein concentration and in vitro dry matter digestibility(IVDMD) of rape showed a sligt decrease at the late harvest compared with the early harvest, but a marked decrease was found in oats at the late harvest. The nitrate concentration of rape was very variable between the cultivars at the both harvesting dates and no clear trend was detectable. Results indicate that the higher yield potential and the higher IVDMD of rape in comparison with oats warrant consideration of rape for use a supplemental autumn forage in Korea.