Although cereal grains are the preferred food plants of the cereal leaf beetle, Oulema melanopus (L.), several other graminoid species are acceptable feeding hosts of larvae and adults of this chrysomelid beetle. In view of the potential for expanding the use of diverse endophytic fungi (Neotyphodium Glenn, Bacon and Hanlin) to protect forage and cereal grasses from insect pests, more information on the effect of Neotyphodium-infected (E ) grasses on the behavior and performance of the most important graminoid pests, including O. melanopus, is required. In feeding and oviposition choice experiments, adult O. melanopus fed readily on E and uninfected (E−) plants of wild tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire) and alpine timothy (Phleum alpinum L.), while exhibiting a feeding preference for E− over E plants of one tall fescue accession. In larval survival and development experiments, low survival on E plants of alpine timothy and one tall fescue accession (averaged 3.75 - 12.5%) was not linked to slow development of surviving larvae because developmental periods were similar on E− (averaged 11.31 - 12.73 days) and E (11.33 - 11.7 days) plants. Larval mortality was 100% on E plants of tall fescue from Morocco. Thus, O. melanopus feeding and survival is significantly reduced on some E wild grasses. Our results also expand our knowledge of the antiinsect properties of fungal endophytes in diverse grasses for possible use in protecting forage and cereal grass cultivars from O. melanopus and other important pests.