Better understanding of genotype and environment interaction will help to optimize yield and quality of crops. The objective of this study was to partition the phenotypic variance of yield and quality traits in broccoli into component sources associated with genotype, environment and genotype by environment interaction. In addition, compare the patterns of stability across environments. Three broccoli genotypes have been evaluated in three different growing seasons for yield and both nitrate and vitamin C content. The results revealed a phenotypic variation in all studied traits among broccoli genotypes. A greater proportion of the phenotypic variation was associated with differences among environments. Analysis of variance uncovered a significant effect of genotypes for yield and chemical quality traits which indicates the existence of a high degree of genetic variability in the tested genotypes. Genotype by environment interaction was significant for yield and chemical quality traits indicating that these traits are modified to different levels by the environments where they grown and emphasis on  the need for testing genotypes in multiple environments to obtain reliable results.  The stability analysis revealed that different degrees of stability are existed among genotypes for yield and chemical quality.