The chemical composition of oats has been poorly studied in Brazil. Therefore, the objective of this study was to characterize the main chemical constituents of Brazilian oat cultivars. This knowledge is essential for the utilization of this cereal in balanced diets, specially for individuals with high blood cholesterol, where the beta-glucans contribute to it's reduction. The analyzed genotipes were recommended by the Brazilian Oat Research Commission. The cultivars studied (CTC3, UFRGS7, UFRGS14, UPF7 and UPF16) showed high levels of protein (16.8%), lipids (6.84%) and beta-glucans (4.89%). The aminoacid profil of these samples was limiting only for lyisine, threonine and isoleucine. The other aminoacids had similar values to those recommended by the FAO. It was observed that all the studied variables suffered changes according to the interactions between genotype, locality and year of production. Cultivars UFRGS14, UFRGS7 and UPF16 were differentiated for their high contents of protein, lipids and beta-glucans, respectively.