Technical Abstract: Annual forages were grown in the Central High Plains of the USA in both irrigated and dryland trials and the harvested forage was analyzed for forage composition and energy concentration. Three spring cereal crops (oats, barley, and triticale), three legumes (peas, soybeans, and vetch) and five summer annuals (forage sorghum, sorghum x sudangrass hybrids, sudangrass, pearl millet, and foxtail millet) were evaluated. Cultivars of these groups were harvested in a single cut system after cereals and summer annuals had produced seed heads and legumes were in early bloom or pod-fill stages of maturity. For all harvested forages, ruminal undegradable intake protein (UIP) was generally in a range of 5 to 10% of crude protein (CP) for samples cut fresh and frozen. These values were slightly lower than UIP levels suggested by National Research Council (1996) for fresh grass and legume forages. Energy values of these forage crops were all similar. The means for digestibility (IVDMD) were similar within crops and management systems, but tended to be lower for summer annuals in irrigated trials compared to dryland trials. Annual forages with adequate feed quality can be a primary source of nutrients required by growing beef cattle or by beef cows in various stages of gestation and lactation. All the forages evaluated in this trial had adequate Total Digestible Nutrients (TDN) values but depending on the forage, some supplementation would be needed for CP and some minerals. Nitrate nitrogen values exceeded safe levels for millets grown with high N fertilizer rates.