The purpose of the investigation was to study the effects of variety properties of oat cultivars and environmental conditions on physical traits and chemical composition of grain and flour. Nine oat cultivars had been grown in the experimental plots (stations) located in two experimental stations in Jelenia Góra and Bobrowniki. The samples were collected in two harvest years. As it has been found, the genetic factors affected physical traits of the grain. The chemical composition of oat grain depended to a large extent on the weather conditions during the growing season. The genetic factors affected only total protein content of the oat grain. The grain of the oat cultivars under investigation was high in total protein but low in starch. Its proteolytic and amylolytic activities were on average levels. Total protein and pentosan content as well as proteolytic activity of the oat flour were lower than those of grain, but starch content and the falling number were higher.