Technical Abstract: Each fall, millions of calves are assembled from farms across the southern U.S. and transported to Oklahoma for growth and development before entering regional feedlots for finishing. Some of these calves come from the Gulf Coast region where genetic adaptation to tropical conditions is advantageous. Although tropically adapted beef breeds may not be able to withstand the winter conditions in Oklahoma as well as the temperate beef breeds, they may be genetically predisposed to consume larger quantities of low quality hay. Beef calves (average weight = 303 kg) of four different genotypes, born and reared at the Subtropical Research Station, Brooksville, FL, were transported to El Reno, OK, in the fall of 2000. Calves were individually fed and had ad libitum access to mature native prairie hay with and without 225 g of supplemental protein/day in a single switch-back design. Providing supplemental protein increased (P=0.02) hay intake (5.44 to 6.06 kg/d) equally across all four genotypes. However, increasing the percentage of tropical breeding in stocker calves from 25% to 100% did not increase hay intake.