Purveyors of the “balance” approach to soil nutrient management have claimed improved chemical and physical grain quality. We evaluated the chemical composition and physical quality of corn grain from two field trials where yield responses to P and/or K fertility had been observed. We found a yield response to P at both locations and to K at one location. Leaf P and K were responsive to fertility levels at both locations. Grain P was responsive to fertility at both locations, but grain K was generally unresponsive. Average kernel size was reduced by P and K stress to the corn crop. Physical grain quality, measured by subjecting a 50-g sample of grain to the Wisconsin Breakage Tester, with all samples pre-equilibrated to the same grain moisture, was not significantly influenced by the P and K fertility treatments. We conclude that yield-limiting P stress significantly influenced corn grain P concentrations (as expected), but neither P or K stress significantly influenced corn grain physical resistance to a breakage test.