This study was aimed to determine forage value of quinoa at the different sowing dates under semi-arid conditions. Research was conducted according to randomized complete blocks design with three replicates in Harran plain conditions in 2016, Sanliurfa, Turkey. Q-52 Quinoa (Chenopodium quinoa Willd.) variety was used as plant material. In the study 9 different sowing dates were used such as 15 February, 1 March, 15 March, 1 April, 15 April, 1 May, 15 May, 1 June and 15 June. In the research plant height, stem diameter, number of branches per plant, biomass yield, dry forage yield and harvest index were investigated. As a result of the research, statistically significant differences were seen between sowing dates at tested characteristics (P≤0.01). As a result of the research, statistically significant differences were seen between sowing dates at tested characteristics (P≤0.01). Plant height ranged from 81.8 cm to 109.4 cm, stem diameter from 9.0 mm to 12.6 mm, number of branches per plant from 10.3 to 12.7 number. The highest biomass yield was obtained from 1 April sowing date with 1751.40 kg da-1 whereas the lowest biomass yield was seen at June 15 sowing date with 1295.28 kg da-1. Dry matter yield values were between 415.8 (15 February) and 546.88 kg da-1 (1 April). Harvest index values were between 39.3% and 42.0%. Quinoa yield characteristics in generally increased from 15 February to 1 April sowing dates, but after 1 April sowing dates decreased. Higher values were obtained from April and May sowing dates. The most suitable planting date for quinoa plant in semi-arid climatic conditions was determined as 1 April and can be recommended in similar ecologies.