The antioxidative properties of oat oil and its fractions were studied using the Rancimat method and lard, tallow and soybean oil as substrates. Oat oil extracted with isopropanol increased the induction time of oxidation of lard and tallow from 2 to 8‐fold compared with the corresponding times without antioxidants, when applied at 1.0 to 5% concentrations. The same increase in stability was achieved with 0.25 to 1.5% concentrations of the separated fractions. The most effective fraction was the lecithin fraction isolated by supercritical CO2 extraction. Almost equal results were achieved with a single‐step ultrafiltration. Effects on the stability of soybean oil were similar but weaker.