Due to the high antioxidant activity of oak fruits, the partial substitution effects of wheat flour (WF) or corn flour (CF) with oak flour (OF) have been investigated. WF or CF was replaced by OF at levels of 0%, 15%, 30%, and 45% in the biscuit formulations to prevent the spontaneous oxidation of lipids, and the characteristics, including peroxide value, antioxidant activity, and sensory properties, were evaluated during 28 days storage. According to the results obtained, biscuit samples with higher OF percentage had higher antioxidant activity and less peroxide value. In terms of sensory evaluation, no adverse effect was observed in the samples containing OF. Therefore, it could be introduced as a good natural source of antioxidant compounds for use in food formulations.