This investigation was conducted at the plastic greenhouses at Qaha Res Farm, Horticultural Research Institute, Qalyubia Governorate, Egypt, to estimate GCA and SCA effects of 7 parents and 21 cross combinations resulting from diallel (Method 2) during the growing winter season of 2020 / 2021 in two different planting time. Also, mean squares due to parents, crosses and par. vs. cross were highly significant for all features in each planting time, except the parents vs. crosses for fruit length, fruit diameter, and no. of fruits per plant at first planting time under various greenhouse conditions. Variance due to GCA were much higher than those of SCA for all studied traits at two planting dates 
revealing the predominance of additive genetic effect in the inheritance of these traits, except fruit length. P2, P3, P5 and P7 seemed to be the best GCA combiner for most of fruit, yield and its attributed traits under all environments, respectively. For most of studied traits, the following crosses; P1 X P4, P4 X P5, P4 X P6, P1 X P5, P3 X P7, P3 x P5, P4 X 
P6 and P5 X P6, had the highest values of SCA effects, respectively. From the previous results, it could be recommended to use the mentioned hybrids to improve winter squash productivity and fruit quality attributed under greenhouse condition.