Technical Abstract: Growing complementary plant species is an alternate approach to enhancing pasture production. Our objective was to estimate combining ability for various native warm-season grasses and legumes grown in binary mixtures in the field using a diallel analysis of variance. Species studied were big bluestem, Illinois bundleflower, roundhead lespedeza, slender lespedeza, switchgrass, and indiangrass. Significant (P<0.05) general combining ability (GCA) effects were found for forage dry matter yield for Illinois bundleflower (-1,232 kg/ha), roundhead lespedeza (-3,453 kg/ha), slender lespedeza (-3,298 kg/ha) and for switchgrass (8,369 kg/ha). Significant specific combining ability (SCA) effects were found for switchgrass-legume mixtures (1,358 kg/ha) and for indiangrass-Illinois bundleflower mixtures (1,225 kg/ha). Significant GCA and SCA effects were found for crude protein concentration (CPC) and in vitro dry matter digestibility (IVDMD). GCA effects for CPC were shown for all species and averaged from -29.6 g/kg for switchgrass to 37.5 g/kg for Illinois bundleflower. SCA effects for CPC were significant for all species combinations. Among grass-legume mixtures, SCA effects for CPC were all negative and averaged -12.8 g/kg. GCA effects for IVDMD averaged from -41.3 g/kg for switchgrass to 18.1 g/kg for slender lespedeza. We found that DM yield alone was not enough to predict compatibility. Other variables, such as CPC and IVDMD helped identify compatible species. Under these experimental conditions, a mixture of indiangrass-Illinois bundleflower was superior to other mixtures.