A 3-year diet study was conducted in two pastures on the Jornada Experimental Range in the northern Chihuahuan Desert, Dona Ana County, New Mexico, USA to compare diets of Raramuri Criollo and Angus x Hereford crossbreed cattle. Fecal samples were collected directly from cattle and analyzed with both Operational Taxonimic Units (OTUs) and Exact Sequence Variants (ESVs). ESVs performed better than OTUs at discriminating between plant taxa. Although patterns of plant preference between the two breeds were not necessarily constant over time, Criollo diets were were found to have proportionally more Honey mesquite (Prosopis glandulosa) and proportionally less Black grama (Bouteloua eripoda) than Angus x Hereford crossbreeds. In general, both breeds consumed proportionally more grass in the winter than in the summer. However, the grass component for both breeds decreased over time, likely due to persistent drought which caused less grass production and availability. Both breeds behaved the same way by replacing the grass component with forbs in the summer and with shrubs in the winter. This study is an example of how fecal DNA analyses can illustrate how livestock alter their diets to cope with drought.