Due to the rise in antibiotic resistance, Enterococcus infections are a major health crisis that requires the development of alternative therapies. Phage therapy offers an alternative to antibiotics and has shown promise in in vitro and in early clinical studies. Here we isolated 18 Enterococcus phages from Southern California wastewater, characterized their host range against a collection of 19 clinical E. faecalis and E. faecium isolates, and sequenced their genomes. We showed that cocktails of two or three phages often prevented the growth of phage-resistant mutants, and identified which phages were replicating the most in each cocktail. When resistant mutants emerged in response to single phages, they showed consistent accumulation of mutations in exopolysaccharide synthesis genes. These data serve to demonstrate that a cocktail approach can inform efforts to improve efficacy against Enterococcus isolates and reduce the emergence of resistance.