Biological invasions by new species can potentially cause widespread changes in the ecological structure of a reef community including competition with indigenous species. Although their native ranges occur in the western Pacific and Indian Oceans, the red lionfish (Pterois volitans) and the devil firefish (Pterois miles) currently comprise an invasive lionfish species complex ranging from the Greater Caribbean seasonally to Maine. We focused on dietary description of Pterois sp. in Broward County, Florida due to limited information on the current invasion in the southeastern Florida reef system. Stomach contents were collected from individuals collected within a 6 km area off the coast. Dietary preference was determined using percent number, percent occurrence and percent weight, as well as the composite index of relative abundance. A shift in depth preference of lionfish was also recorded. Seasonal variance was studied and a shift in prey preference was discovered throughout the four quarterly sampling periods. A high percent teleost diet was documented during the third quarter (July-September) and a high crustacean diet in the fourth quarter (October-December). There was a 38% change in the amount of teleost prey present between the sampling events. We observed an ontogenetic shift from a mainly crustacean diet to one consisting of mainly teleost fishes: the smallest size group (5-10 cm) had a 100% crustacean diet, whereas the largest size group (35-40 cm) had a 77% teleost and 23% crustacean diet. This trend was also found to be independent of depth. This change in trophic preference in relation to size was the first documentation of this trend in Broward County, Florida.