We examined the feeding strategy of the extinct hypsodont antilocaprid Stockoceros onusrosagris through an analysis of tooth mesowear and microwear and compared it to available data on the extant pronghorn Antilocapra americana. The mesowear pattern of both pronghorns is very similar. Molar teeth display relatively sharp apical cusps with slightly rounded extreme tips characteristic of a relatively low-abrasion diet. While S. onusrosagris displays a slightly more abrasive mesowear pattern than A. americana, the difference is not statistically significant. Microwear analysis, however, firmly places S. onusrosagris with extant mixed feeders, while A. americana has microwear typical of extant browsers. Our observations suggest that S. onusrosagris incorporated more grass in its diet than the modern pronghorn and browsed and grazed on a regional or seasonal basis. The fact that the mesowear pattern in S. onusrosagris shows relatively little abrasion may suggest that grasses taken may have been C3 grasses. Results of this study may shed light on the extreme hypsodonty seen in the modern pronghorn despite the fact that it consumes relatively soft food items.