The objective of the Conservation Reserve Program (CRP) is to convert erodible cropland to perennial vegetation. Under severe drought, CRP land is frequently utilized for grazing; thus, there is a need to better understand trends in forage nutritional quality in species used in CRP plantings. This study evaluated 13 cool-season irrigated and dryland grasses from May to August and regrowth from September to November in northern Utah during 2004 and 2005 for crude protein (CP), neutral detergent fiber digestibility (NDFD), in vitro true digestibility (IVTD), and neutral detergent fiber (NDF) values. Species, sampling date, year, and sampling date × species interaction had a significant (P < 0.05) effect on CP, NDFD, IVTD, and NDF values. From May to August, there was a strong linear decline in CP, NDFD, and IVTD values. Mean CP values ranged from 68 to 251 g kg^-1 in all species examined. Orchardgrass, smooth bromegrass, RS-hybrid, and crested wheatgrass had CP, NDFD, and IVTD values similar to orchardgrass and timothy, but less than perennial ryegrass. Crested wheatgrass had NDF values similar to timothy, but less than orchardgrass. Crested wheatgrass and smooth bromegrass had the greatest nutritional quality and were often similar to orchardgrass, tall fescue, and timothy.