This work was carried out at Tag El-Ezz Agriculture Research Station, El-Dakahlia Governorate during 2005/ 2006 and 2006/ 2007 seasons to study the effect of harvesting dates i. e. 50, 60, 70 and 80 days after 50% heading on yield, yield components, seed germination, seedling vigour traits and its chemical composition (protein, carbohydrate) contents of some wheat cultivars i. e. Sakha 93, Giza 168, Gemmiza 9 and Gemmiza 10. The results revealed that. Harvesting wheat after 50 to 70 days from 50% heading increased gradually both of grain yield/ feddan, 1000- grain weight and quality characters of seed, namely germination percentage and germination rate, plumule and radical length, seedling dry weight, seedling vigor index, carbohydrate content and germination after seed aging in both seasons. However, delaying harvest to 80 days from 50% heading decreased moisture content and electrical conductivity of seed. Harvesting Plants at 50, 60 and 80 days after 50% heading reduced grain yield 60.84, 16.24 and 3.91% in the first season and 64.17, 18.96 and 5.08% in the second season, comparing with harvest at 70 days after 50% heading in both respective seasons. Wheat cultivar Giza 168 surpassed the other cultivars in grain yield/ fed., 1000-grain weight, germination percentage and germination rate, germination after seed aging, electrical conductivity and protein content in both seasons, while, wheat cultivar Gemmiza 9 surpassed the other cultivars in plumule and radical length, seedling dry weight, seedling vigour index and carbohydrate content in both seasons. The interaction between harvesting dates and wheat varieties had significant effects on all the most studied characters. At 70 days after 50% heading, wheat variety Giza 168 recorded the highest grain yield (21.92 and 21.69 ardab/ fed.), 1000-grains weight and germination percentage and rate. ِِِAt 80 days after 50% heading, wheat cultivar Gemmiza 9 gave the highest seedling dry weight and seedling vigour index, while Giza 168 gave the highest germination after seed aging. Positive correlations were observed between harvesting dates and the most wheat traits except for seed moisture content and electrical conductivity. In conclusion, wheat cultivars can be harvested after 60 to 70 days after 50% heading with obtaining high yield and good seed quality.