Seventeen genotypes (G) of bread wheat (14 promising lines and 3 commercial cultivars) were evaluated for mean performance and stability of grain yield/plant, grain protein content and dry gluten percentage under 16 environments (two locations (L), two sowing dates(D) and four fertilization treatments (F)). The resultsconfirmed the existence of considerable genetic variation among genotypes and their performance was significantly affected by different environments for the studied traits. Kalubia locations recorded the highest mean values for grain yield/plant while; Fayoum location recorded the highest mean values for the two quality traits. Yield and quality traits were significantly increased on early (recommended) sowing dates at Kalubia and Fayoum locations than on late sowing dates. Applying biofertilizer only gave the lowest mean performance in all traits, but adding mineral N besides biofertilizer markedly increased grain yield/plant and the two quality traits. However, insignificant differences existed between the rate of nitrogen recommended (80kg N/fed.) and the rate of (biofertilizer + 60kgN/fed.), indicating that biofertilizer could be efficient in reducing costs of the expensive mineral N and reducing environmental pollution. On an average highest values of grain yield/plant were recorded by the promising wheat lines no. 10 (24.57 g), no. 9 (22.50 g), and no. 11 (21.64 g) as compared to the best check cultivar Giza 168. Meantime, this cultivar surpassed the other genotypes in protein and dry gluten percentages. Concerning phenotypic stability, the three superior lines no. 10, 9 and 11 gave the highest mean values (x¯) of grain/plant coupled with significant regression coefficient (bi) values higher than unity and significant deviation from regression (S²di), thus they considered specifically adapted to favourable environments.