Legumes have the potential to provide high-quality pasture but are rarely grazed by horses in monocultures. The objectives of this research were to evaluate yield, forage nutritive value, and preference of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and white clover (Trifolium repens L.) in monoculture or in mixture with perennial cool-season grasses under horse grazing. Research was conducted between 2014 and 2016 in St. Paul, MN. Two separate but identical experiments were established in spring 2014 and 2015. Four to six adult horses grazed legumes, which were established as a randomized complete block design with and without cool-season grasses in four replicates. Forages were measured for yield, forage nutritive value, and preference every 28 d during the grazing season. Averaged over both experiments, alfalfa, red clover, and white clover yielded 13.4, 6.9, and 4.5 Mg ha–1 yr–1, respectively. In grass mixtures, alfalfa, red clover, and white clover yielded 13.1, 9.4, and 8.6 Mg ha–1 yr–1, respectively. Equine digestible energy (DE) of all legumes in monoculture or mixture exceeded the energy requirements for adult horses at maintenance with ³2.29 Mcal kg–1. Red and white clover were more preferred by horses than alfalfa, and preference was positively correlated to crude protein and equine DE. This research helps confirm that legumes are high in nutritive value, yield well, are a preferred forage option for horses, and should be considered as a viable grazing option for horses with increased energy and nutritional needs.