Barred Owls (Strix varia) continue to expand through the Pacific Northwest and into the Sierra Nevada, California, threatening native species. In this study, we conducted genetic-based dietary analyses using intestinal samples from invasive barred owls collected at the front end of their California expansion to better understand potential impacts on wildlife communities. Using a diverse panel of DNA amplifying primers and high-throughput-sequencing, we successfully screened the intestinal contents of 124 barred owls, detecting a broad diet of 78 unique prey types (48 vertebrates and 30 invertebrates). Commonly consumed taxa of note included Douglas squirrel (Tamiasciurus douglasii), Northern flying squirrels (Glaucomys sabrinus), Sierra and Pacific tree frogs (Pseudacris sierra and P. regilla), dusky footed woodrats (Neotoma fuscipes), and several game and domestic species. Barred owl prey consumption demonstrates the potential for exploitative competition with spotted owls (Strix occidentalis), but also potential competition with sensitive species including fishers (Pekania pennanti) and Northern goshawks (Accipiter gentilis). Diet composition varied across an elevation gradient, based on forest conditions, and between the Sierra Nevada and Klamath regions. Our findings indicate that barred owls – as generalist predators – will not serve as ecological replacements for spotted owls should they continue to increase in relative abundance.