ABSTRACTThe three main oat avenanthramides, N‐(4′‐hydroxy)‐(E)‐cinnamoyl‐5‐hydroxyanthranilic acid (Bp), N‐(4′‐hydroxy‐3′‐methoxy)‐(E)‐cinnamoyl‐5‐hydroxyanthranilic acid (Bf), and N‐(3′,4′‐dihydroxy)‐(E)‐cinnamoyl‐5‐hydroxyanthranilic acid (Bc), and their corresponding cinnamic acids, p‐coumaric (P), ferulic (F), and caffeic (C), were investigated for stability to pH, temperature, and UV‐light treatment. The retention of the avenanthramides after processing of oat‐based food products was also analyzed. The avenanthramide Bc and the cinnamic acid C were sensitive to alkali and neutral conditions, especially in combination with heat treatment, whereas the other compounds studied were more stable. The cinnamic acids but not the avenanthramides were isomerized when irradiated with UV‐light. The avenanthramides were restored after processing of oat‐based products.