A field experiment was carried out to study the effect of date of sowing and seed rate on onion cv. N- 53 sets at nursery under Sub-humid Southern Plain and Aravalli Hills at Rajasthan College of Agriculture, MPUAT, Udaipur, Rajasthan, during years 2010 and 11. The experiment consisted of 9 treatment combinations comprising of three dates of sowing viz., 12th Feb. (T1), 22nd Feb. (T2) & 4th March (T3) and three levels of seed rate viz., 20 g (S1), 25 g (S2) and 30 g (S3) per m2. These treatment combinations were evaluated under factorial randomized block design with 4 replications. The results revealed that sowing of onion seeds on 12 February (T1) brought significant increased in sets diameter (1.87 cm) and sets weight (2.50 g) and also obtained maximum standard grade sets i.e. 1.5-2.0 cm (34.17 %) as compared to later dates of sowing. Further, significantly higher sets diameter (1.98 cm) was obtained with S1 treatment (20 g per m2), Similarly, seed rate @ 25 g per m2 recorded maximum sets weight (1.99 g) and standard grades (1.5- 2.0) sets (20.83 %) over other seed rates. Whereas, the interaction T1S1 (sowing on 12 Feb. with 25 g seed per m2) recorded maximum standard grade (1.5- 2.0) size sets (42.50 %).