Quality protein maize (QPM) cultivars contain higher levels of lysine and tryptophan as compared to non-QPM counterparts, and can minimize the risk of protein malnutrition among communities increasingly dependent on maize as their food staple. This study was undertaken to assess the performances of QPM hybrids, and estimate heterosis and combining ability effects of highland QPM inbred lines for grain yield, agronomic and protein quality traits. Hybrids of 20 inbred lines and two testers, and the parental lines were evaluated across three locations in Ethiopia. Significant variations were observed among the parents and the hybrids for almost all measured traits that allows the selection of preferred inbred lines and hybrids. Several hybrids showed desirable heterosis for most studied traits. Mean squares attributable to general (GCA) and specific (SCA) combining ability effects were significant for most traits. However, the contributions of GCA sum of squares to the variation among the hybrids were larger than SCA sum of squares, suggesting that the traits were conditioned mainly by additive gene effects. Inbred lines L12, L17, L19, and L20 had desirable GCA effects for grain yield, whereas L12 and L13 were the best general combiners for protein quality traits. Hybrids L17 x 142-1eQ and L20 x 142-1-eQ showed most desirable perse performances and SCA effects for grain yield. Based on grain yield SCA effects, most inbred lines used in the study were grouped into distinctive heterotic patterns. This study indicated the possibility of developing highland QPM germplasm with acceptable grain yield, agronomic and protein quality traits.