The objective of the investigation study was to assess the antioxidant properties of the whole oat grains, husk, endosperm, and bran. The investigation material was oat grain of the following cultivars: Arab, Bohun, Celer, Cwał, Deresz, Furman, Kasztan, Krezus, Polar, and Rajtar. The content of polyphenol in the milling fractions investigated was measured using a Folin-Ciocalteau method. Additionally, the ability to eliminate an ABTS^•+ free radical was analyzed. The highest polyphenol levels were found in the husk of the oat cultivars investigated. Smaller amounts were found in bran, whole grain, and endosperm, respectively. This is significantly correlated with the radical scavenging activity of individual milling fractions of the material investigated.