The 30 days old healthy seedlings of three varieties of summer squash viz. V1: Bulam House, V2: Cora F1 and V3: Chungma Zucchini raised in poly bags during three consecutive spring seasons from 2005 to 2007 were transplanted on five planting times at fortnightly intervals viz. P1: February 16, P2: March 01, P3: March 16, P4: April 01 and P5: April 16 in a randomized block design with three replications every year at a spacing of 90x60 cm having plot size of 2.70x2.40 m with a population of 12 plants per plot. The recommended doses of manures and fertilizers and all agronomic practices were adopted timely for raising a healthy and normal crop. The data on yield (q/ha), average fruit weight/size (g), number of fruits per plant, plant height (cm) and days to maturity were recorded. Significant differences were recorded for all the traits studied during all the three years. The maximum yield (766.2 q/ha), average fruit weight/size (1320.4 g) and number of fruits per plant (22.6) were produced by planting the variety Cora F1 on February 16. The delay in planting reduced the yield, its attributes and also days to maturity. It is concluded that summer squash variety Cora F1 planted in mid February gave the highest yield followed by Chungma Zucchini  under the low hill conditions.