The Chihuahuan desert ecosystem has experienced a decrease in black grama, a perennial grass species with high ecological value for protecting desert topsoil, along with a subsequent increase in mesquite. This trend is thought to be due to several management- and environment-related factors. We compared diet selection of a heritage Raramuri Criollo (RC) vs. Angus-X-Hereford (AH) cattle, typical of the region, using fecal DNA metabarcoding by a commercial laboratory to determine the proportion of black grama and mesquite in samples. RC and AH cows grazed two adjacent pastures (~1100 ha) separately, switched at the mid-point of each period. Rectal fecal samples collected from 10 cows per breed each period. The study was replicated across seasons (growing and dormant) for three consecutive years (240 total fecal samples) in a completely randomized design. Relative abundance of plant species was ranked over the entire study and by season. The MIXED procedure of SAS 9.4 was used to analyze the relative proportions of black grama and mesquite in fecal samples by breed, season, year, and all interactions. Black grama was a more important forage resource than mesquite (ranked 8 vs. 11), particularly during dormancy (ranked 3 vs. 7). When examined by breed, AH had twice the percentage of black grama vs. RC (P<0.05) and even more so during the dormant season (P<0.05). In contrast, RC fecal samples tended to contain a higher percentage of mesquite (P=0.05). Adjustments for dry matter intake (relative to BW) by breed (545 vs. 350 kg mean BW for AH vs. RC respectively) suggests that AH consumed 3.09 fold more black grama while RC consumed 1.59 times more of mesquite. Differences in diet composition documented in this study support the hypothesis that RC cattle could impose a lighter grazing pressure on the black grama community and potentially be utilized as a conservation tool on Chihuahuan Desert rangeland.