This study estimated the effect of sowing and harvesting dates on dry matter (DM) yield and feed value of forage oats at Sancheong, Korea. The forage oats (Darkhorse vs. Highspeed) were used in this experiment. The experimental main plots consisted of the different sowing and harvesting dates at 2 seasons as follows: spring oats of sowing (February 25, March 3 and March 13) and harvesting (May 27, June 6 and June 16); and fall oats of sowing (August 15, August 25 and September 4) and harvesting (October 15, October 25 and November 4). On spring oats, Highspeed sown on March 3 and then harvesting on June 6 had the highest (p<0.05) plant length and DM yield. Crude protein content decreased (p<0.05) in seed of the delayed-harvesting Highspeed. On fall oats, plant length and DM yield with the delayed-harvesting date increased (p<0.05), while crude protein content of the delayed-harvesting Highspeed decreased (p<0.05). This study concluded that the spring oat sown in early March and then harvesting in early June was recommended to increase dry matter and feed value although the fall oat sown in end August and then harvesting in early November was recommended for fall period.