The objective of this study is to determinate the optimal growth stage for applying supplemental irrigation and nitrogen to enhance bread wheat (Triticum aestivum L.) productivity and water use efficiency under rainfed condition in Morocco. Field trial was conducted during two years (2007-2008 and 2008-2009). Three genotypes (G) of Moroccan bread wheat; Achtar, Arrehane and an Advanced Line II were combined with five nitrogen doses (N); 0, 40, 80, 120 and 160 kg N ha–1 and three water treatments (I); rainfed (I0), irrigated (60 mm) at 21 according to the Zadoks scale (I1) and irrigated (60 mm) at 59 according to the Zadoks scale (I2). Results in the drought year (2007-2008) show that I2 improves water use efficiency, grain yield and its components by 91 and 60% respectively, compared to I0 and I1 treatments. I2 has limited the effects of the Chergui –hot and dry wind coming from the Sahara- which has a negative impact on growth mainly at the end of the cycle of the crop. Grain yield and other yield components increased simultaneously with the increase in nitrogen inputs during the second 2008-2009 crop year which was rainy. The 120 kg N ha–1 dose allowed the highest results, with no significant difference with the yield obtained after a 160 kg N ha–1 input. Genotype appeared to have no significant effect neither on grain yield nor on water use efficiency in both the years.