Grain protein (GP) is an important property linked to the leavening capacity of wheat (Triticum aestivum L.) flour, and is associated with nitrogen (N) fertilizer management. Early vegetative stage applications of N increase grain yield (GY), while late (near heading) applications have been suggested in order to enhance GP. In this study, field experiments with soft winter wheat (red and white) were conducted at four locations over three years to study GP response to late N fertilization (0, 22.5 and 45 kg N/ha) and the interaction of that response with: a) the Feekes 3-5 fertilizer N rate (84, 118 and 151 kg N/ha); b) the timing of late N fertilization (Feekes 9, Feekes 10, Feekes 10.1 and Feekes 10.5); c) the previous crop (soybean (Glycine max (L.) Merr.) and corn (Zea mays L.)); and d) the wheat cultivar. Nitrogen added at Feekes 3-5 increased both GY and GP, but the effect on GY was greater. Soybean was the better previous crop as GY was higher, but there was no effect of prior crop on GP. Generally, late N did not influence GY, but there greater GY with late N was found at two locations. The GP increased by about 10 mg N per g of grain dry matter with a late N rate of 45 kg/ha. Late N could be delayed until Feekes 10.5 without greatly affecting the GP response. The GP response to late N rate and timing were similar across the two red and two white cultivars used.