Warm-season grasses have shown great potential for biomass production. However, their productivity under irrigated conditions has not been thoroughly documented. This study evaluated the biomass production potential and production stability of a number of warm- and cool-season grasses across an irrigation gradient. Under the multiple-harvest management strategy, the cool-season grasses were most productive across the entire growing season. Nevertheless, when considering only the summer harvests, the switchgrass and big bluestem entries were the most productive, although the lowland cultivar Alamo did not perform well under the conditions. Overall, cool-season grasses were clearly the most productive for total biomass production across the growing season. However, based on the high biomass production of switchgrass, this species may have potential as a high-producing option for animal feed during the summer months when the cool-season grasses are unproductive.