A diversity study was carried out to genetically characterize 375 oat landraces (Avena sativa L. And Avena byzantina K.Koch) collected from Turkey and preserved in different gene banks. New assays interrogating oat-based microsatellite and single nucleotide polymorphism loci were used to characterize the landraces. The assays interrogated 176 alleles at 68 loci with an average of 4.5 alleles per locus. The polymorphism information content of the simple sequence repeats was relatively high with a mean value of 0.76. The first two principal components from the principal component analysis (PCA) separated two groups of accessions and explained 9.3% of the variation in the marker data. When the accessions were divided into two groups based on the first two principal components, the geographic origin matched well with the PCA grouping. Similarly, when classified by plant growth habit, the spring types originated mostly from the highlands of East Anatolia and from inner Anatolia. A heat map constructed based on marker data corresponded to province of origins of the landraces. The landraces with the geographical information are clustered into three major groups based on growth habit: winter, spring, or facultative. Population structure analysis also detected two subpopulations based on allele frequency and indicated a similar grouping with diversity analysis. Crown rust suggested that most of the lines did not contain major resistance genes. Of the landraces tested, only one (TL214) was considered resistant. Overall, this study has provided genetic characterization of unique germplasm from the center of oat domestication, which will be useful to oat breeding programs.