Cattle-grazing in riparian areas has become increasingly controversial. More information is needed about cattle use of these areas to develop Best Management Practices. This study was designed to determine seasonal changes in diet selection of cattle in a montane riparian community in northern Colorado. Previous cattle diet studies in riparian zones have not separated the interaction between seasonal preference and biomass utilization. The experiment was conducted within large exclosures that had not been grazed by livestock since 1956. Vegetation biomass estimates and diet samples from 5 esophageally fistulated steers were taken during 4 grazing periods (spring, early-summer, late- summer, and fall) in 1995. Vegetation measurements and diet samples were also collected during the late summer and fall of 1994. One of the 3 paddocks in each grazing period of 1995 had been grazed in 1994. Steer diets in 1995 were found to contain 15% more Carex spp. from paddocks that had been ungrazed until 1995 as compared with paddocks previously grazed in 1994. Kentucky bluegrass (Poa pratensis L.) and forbs were consumed about 13 times and 5 times greater, respectively, in previously grazed paddocks as compared with ungrazed paddocks. Carex spp. were the most preferred component of cattle diets throughout the study. Willows (Salix spp.) were not preferred in any grazing period of either year, and consisted of less than 4% of cattle diets in any season. However, a trend towards increased consumption of willows was found from spring to fall, 1995. Information obtained in this study should help managers develop grazing systems that allow for a desirable combination of herbaceous and woody species in a riparian community while still affording grazeable forage.