Rancho Cañada de los Vaqueros was a 17,760-acre (71.9 km2) Mexican land grant mostly in present-day eastern Contra Costa County, California, and partially into northeastern Alameda County, California. Los Vaqueros Reservoir, located between Livermore and Brentwood in the Diablo Range, is on and named for the former rancho. Vasco Road passes through the site.