Nitrogen (N) is the nutrient that most often limits maize (Zea mays L.) grain yield and quality. Even under conditions where grain yield is not limited, N can affect composition and quality. The objectives of this study were to quantify and characterize how grain yield, grain quality (kernel weight and test weight) and grain composition (protein, oil, and starch concentrations) of commercial hybrids respond to nitrogen fertilizer. The response of eleven commercial hybrids to N was evaluated in a field experiment during the 2004 and 2005 growing seasons. In 2004 the N rates applied were 0, 170 and 340 kg N/ha, and in 2005 they were 0, 135 and 270 kg N/ha. Nitrogen had a significant (p<0.1) and positive effect on grain yield (7.3, 9.2 and 9.5 Mg/ha on average for the 3 N levels) and protein concentration (67, 84 and 88 g/kg) but a negative effect on starch (740, 723, and 719 g/kg). Genotype had a significant effect on oil concentration (ranged from 37 to 46 g/kg), kernel weight (257 to 296 mg), and test weight (775 to 798 kg/m3). Moreover, there was a significant hybrid X N interaction for grain yield, test weight, oil and starch indicating that the response of these variables to N differed among hybrids. In general, the variance component attributed to growing season was larger than those due to hybrid X growing season or hybrid X N interaction, indicating that while weather does affect productivity and quality, the effects of N and hybrid tend to be relatively consistent across growing seasons. Our data show that hybrid plays a larger role in determining oil, test weight, and kernel weight, while N fertilization (and its interaction with hybrid) primarily impacts grain yield, protein and starch.