A study was conducted to test whether Rocky Mountain elk used invasive species on their winter range, areas of high conservation value that are experiencing high rates of invasion by cheatgrass and spotted knapweed. Five elk populations from western Montana were chosen to test for the presence of invasive species in their diet. Pellet samples from elk rectums were collected during the handling of 12 adult females for a related study or from the field on open prairie flats from February to June. Each sample constituted a composite of two individual pellets selected from 20 pellet groups; this was a sample size of composite samples similar to a previous study, which examined the comparative diet content of ungulates. There were no differences in the quantities of any vegetation classes in elk fecal pellets across seasons, in fact the analysis showed nearly identical use of different plant classes in winter and spring.