Many studies have been performed to demonstrate the antioxidant activities of hydrolyzed proteins and peptides from cereals such as corn, wheat, and barley using in vitro chemical assays. Studies have demonstrated the antioxidant properties of hydrolyzed oat proteins, and seven peptides have been identified including FNDRLRQGQLL (P1), GLVYIL (P2), GQTV (P3), GQTVFNDRLRQGQLL (P4), YHNAP (P5), YHNAPGLVYIL (P6), and DVNNNANQLEPR (P7). The purpose of the current study was to establish the antioxidant activities of these peptides using chemical and cell culture based assays. The current research found that all seven peptides exhibited radical scavenging activity in ORAC assay. Moreover, cytoprotective activities of the P1, P2, P6, and P7 against oxidative stress induced by 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AAPH) have been studied, including alteration of the antioxidant enzymes glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), change in total glutathione and levels of reactive oxygen species (ROS).