Abstract Introduction of high yielding cross bred dairy cattle in the farming system is pushing farming communities to produce high yielding forage crops. The experiment was conducted in 2017 and 2018 cropping seasons for two years at Abera sheep type improvement sub-station with the objective to determine optimum seed rate for high herbage and seed yield. The trial was carried out in randomized complete block design (RCBD) with four replications. Seed rates of 50, 75, 100, 125 and 150 kg/ha were used as treatments. Plant height, stem to leaf ration, DM yield, seed yield and straw yield were significantly affected at (P<0.05) with increase seed rate. The height of fodder oat increased with increasing rate of seed. The highest height value (129 cm) was obtained at seed rate of 150 kg/ha followed by (127.50 cm) at seed rate of 125 kg/ha. Leaf to stem ratio was not significantly affected by seed rate. Dry matter yield was significantly affected by seed rate at (P<0.05) with highest 13.26 t/ha by using seed rate of 125 kg/ha followed by 12.3 t/ha by using seed rate of 1oo kg/h. hence, the DM yield was at seed rates of 50, 75 and 150 kg/ha are significantly different at seed rates of 125 and 150. This could be due to the more competitiveness of oats as weeds at the higher seeding rate and low crop density at lower seed rate. The better seed quality and yield has been recorded at seed rate of 75 kg/ha which is 3.32 t/ha followed by 100 kg/ha which is 3.11 t/ha. Therefore it could be recommended that for those who need to produce seed should use 75 kg/ha of seed rate whereas those who involved in dairy production, should use 100/125 kg/ha seed rate depending viability of seed.