Understanding the impact of small mammals on the development of grasslands requires information on their food preferences. We conducted feeding trials with 4 species of common small mammals, prairie voles (Microtus ochrogaster), meadow voles (M. pennsylvanicus), white-footed mice (Peromyscus leucopus), and eastern cottontails (Sylvilagus floridanus), to determine the relative palatability of plant shoots and seeds in introduced grasslands of east-central Illinois. Because we needed to conduct many feeding trials we developed a rapid method for comparison of palatability of plants to multiple species of small mammals in the field. We evaluated the method by comparison with previous data on food preference and palatability for voles at nearby study sites. Shoots of herbaceous legumes (Medicago sativa and Trifolium pratense) and dandelions (Taraxacum officianale) were among the most palatable foods for voles, and bluegrass (Poa pratensis) was among the least palatable. Meadow voles found palatable more species of graminoids than did prairie voles, and meadow voles, but not prairie voles, found palatable a greater percentage of graminoids than of forbs. A greater percentage of introduced plants than of native plants were palatable to prairie voles, but this likely reflected a high proportion of introduced graminoids among tested plants. White-footed mice found palatable a few forbs and a greater percentage of annual plants compared with perennial plants, whereas cottontails found palatable many forbs and woody plants and a greater percentage of perennial plants. White-footed mice tended to eat larger amounts and more kinds of seeds than voles, and only white-footed mice tended to eat more of large-seeded species. Plant type did not appear to significantly affect palatability of seeds for any mammal. We used these results to predict the likely impact of small mammals on the development of nonnative grasslands.