The present investigation was carried out at Shandaweel Agricultural Research Station, Agricultural Research Center, Egypt, during the three successive seasons from 2004/2005 to 2006/2007. The objectives of the this investigation were to evaluate some bread wheat genotypes under heat stress conditions in Upper Egypt and to identify the most stable genotypes under these conditions. Twelve bread wheat genotypes (Triticum aestivum L) were evaluated under nine environments which are the combination among three sowing dates i.e. 25th November, 10 th December and 25 th December during the three winter growing seasons. Randomized completed block design was used for every planting date. The studied characters included days to physiological maturity, plant height, peduncle length, flag leaf area and straw yield (t/ha). Performance of the twelve wheat genotypes showed different responses to the different environments. The combined analysis of variance showed highly significant differences among planting dates and genotypes for all studied traits. Delaying sowing date reduced days to physiological maturity , plant height, peduncle length, flag leaf area, and straw yield in the second and third planting dates by an average of (6.63 &14.00%), (3.85 & 10.33%), (6.85 & 20.21%), (14.45 & 23.59%) and (17.37& 29.76%), respectively, compared with the recommended sowing date. The joint regression analysis of variance indicated highly significant differences among genotypes for all studied characters. Moreover, partitioning mean of squares due to environments plus genotypes x environments interactions as indicated by E + (G x E) to the following items E (Linear) showed highly significance for all studied traits. Meanwhile G×E component mean squares were highly significant and significant for all studied characters except for peduncle length. The remainder sum of squares were highly significant for all studied characters. Data of heat susceptibility index for straw yield under normal and late sowing dates indicated that six genotypes i.e. Line # 3, Line # 7, Line # 8 Gemmeiza 9, El-Nelin and HD 2501 were tolerant to heat stress (late sowing dates).