Quality Protein Maize (QPM) has improved nutritional quality due to the opaque2 mutation as well as hard endosperm conferred by uncharacterized modifier genes. We have developed a series of QPM inbred lines based on crosses between public U.S. Corn Belt-adapted lines with QPM lines developed at the International Wheat and Maize Improvement Center (CIMMYT). The resulting inbred lines exhibit characteristics of other QPM germplasm including translucent endosperm and elevated concentration of the essential amino acids lysine and tryp- tophan. We characterized the genetic mechanisms con- trolling yield of hybrids made from the QPM inbreds. For machine harvestable grain yield, specific combining abili- ty was significant, while general combining ability was significant only for the inbreds designated as males in the study, suggesting both additive and non-additive genetic effects were important for determining yield of these tem- perate QPM hybrids. Hybrids produced from different QPM donor lines on average had higher yields than hy- brids produced in from the same donor lines, suggesting the combining ability of the QPM donor may contribute to the performance of these hybrids.