We examined seasonal diets of an introduced population of Dama dama dama (European Fallow Deer) on Little St. Simons Island, GA. We analyzed rumen contents from hunter-harvested deer during fall and winter of 2004–05 and 2005–06. Fecal pellets also were collected monthly from November 2004 to December 2005 and examined microscopically for unique plant-cell characteristics. Fallow Deer utilized a variety of food items based on seasonal availability, although mast and browse were the most abundant food items in the rumens examined. Fallow Deer preferred Quercus spp. (oak) acorns, but consumed more Sabal palmetto (Cabbage Palm) fruit when acorns were less abundant. Microhistological techniques underestimated the occurrence of highly digestible items such as mast, but were more effective at identifying grasses and browse. Grasses were the most common and abundant forage class in feces, with peak grass use in the summer (67%). Fallow Deer's ability to utilize a wide variety of food items including low-quality forage has contributed to their success in this barrier island ecosystem. However, low productivity, suppressed body weights, and small antler characteristics are likely due to a low-quality diet and over-population.