The present study was aimed at finding out the genetic control and heritability of days to flowering at application and non application of nitrogen environments (Dp and Ds) and its related stress tolerance indices based on half diallel crosses of six spring oil seed rape varieties and their 15 F2 progenies. Significant mean squares of general and specific combining abilities (GCA and SCA) were observed for Dp, Ds, Mean Productivity (MP), Geometric Mean Productivity (GMP), tolerance index (TOL), stress tolerance index (STI) and Stress Susceptibility Index (SSI), indicating importance of additive and non-additive genetic effects for them. Significant ratio of GCA to SCA mean square and high narrow-sense heritability estimates were exhibited for Dp, Ds, MP, GMP and STI, indicating the prime importance of additive genetic effects. Significant correlation among Dp, Ds, MP, GMP and STI for GCA effects of parents and SCA effects of crosses, indicating the efficiency of these stress indices for improving days to flowering. On compare to SCA effects, most of crosses had significant high parent heterosis for Yp, Ys and all the stress indices, therefore, selection the better combinations based on heterosis will be more effective than SCA effect.