Orchardgrass, or cocksfoot, (Dactylis glomerata L.) is one of the most important forage grasses used in temperate agriculture. Yet, genetic gains are slow and complicated owing to the perennial and autotetraploid nature of orchardgrass. The development of orchardgrass population hybrids may be a way to more efficiently make genetic gains through heterosis. In the study reported herein, we describe the results of a 3 year study of the effect of heterosis on the forage quality of orchardgrass population hybrids managed with supplemental irrigation at a Cache County, UT, USA field site. The population hybrids derived from the orchardgrass cultivars Latar, Paiute, and Potomac; and from six additional germplasm sources from Asia, Europe, and North America. Data reflected July and August harvests from 2008 to 2010 and included crude protein (CP), in vitro true digestibility (IVTD), neutral detergent fiber (NDF), and water soluble carbohydrates (WSC). There were differences (P −1), and August CP (4 g kg−1), IVTD (7 g kg−1), NDF (−9 g kg−1), and WSC (4 g kg−1). Overall, the results suggest that population hybrids may prove a feasible approach for orchardgrass forage quality improvement.