Wild oat tetraploids of the section Pachycarpa have already been proven to be a rich source of useful genes but have largely been unexploited for Puccinia coronata resistance. In this study, accessions of Avena magna, A. murphyi, and A. insularis gathered from European and North American gene banks were evaluated at the seedling stage for crown rust reaction using the host-pathogen test and six highly diverse and virulent P. coronata isolates. Of the 92 Avena accessions analyzed, 58.7% were resistant to at least one crown rust race. In all, 37% of the tested accessions reacted nonuniformly, which indicated their heterogeneity. The highest level of resistance was observed in three of the accessions, one of which was verified by flow cytometry as being hexaploid and two of which were verified as being tetraploids. The infection profiles of 19 accessions corresponded to resistance determined by the genes Pc14, Pc39, Pc40, Pc48, Pc50, Pc54, Pc55, Pc61, Pc67, Pc68, Pc97, Pc101, or Pc104. The patterns of infection of the remaining resistant A. magna and A. murphyi accessions allowed us to postulate the presence of potentially novel crown rust resistance genes.