White-tailed Deer (Odocoileus virginianus) have been shown to be detrimental to a number of Lepidoptera. Potential host plants for specialist butterfly species can be reduced and removed from native areas through deer browsing. The Ozark Baltimore Checkerspot (Euphydryas phaeton ozarkae) is a univoltine nymphalid butterfly endemic to the Ozark regions of Arkansas, Kansas, Missouri, and Oklahoma. In the area around the Buffalo River in Arkansas, the larval host for this butterfly is Smooth Yellow False Foxglove (Aureolaria flava). We examined the timing and quantified the effect that deer foraging had on A. flava in four E. p. ozarkae populations. Browsing occurred in late spring and reduced plant availability by as much as 87% over a two-month period. Browsed plants lost an average of 44 cm in height; data show taller plants were more likely to be browsed than shorter ones. Extensive herbivory caused early-fall-active and late-spring-active larvae to contend with reduced host plant availability, which likely resulted in increased mortality. We also found that browsed plants were less likely to be selected for oviposition. The amount of plant loss appeared to be associated with deer abundance and area attributes (i.e., slope, human activity, plant density, etc.). We found that browsing by White-tailed Deer that is too intense or prolonged can have important consequences for the Ozark Baltimore Checkerspot.