The antioxidative effect of dietary supplementation with oregano essential oil on susceptibility of raw and cooked breast and thigh muscle meat of chickens to lipid oxidation during refrigerated storage for 9 days was investigated. Day-old chickens (n=80) were randomly divided into four groups and fed a basal diet containing 30 mg α-tocopheryl acetate kg(-1) feed as control, or basal diet plus 200 mg α-tocopheryl acetate kg(-1) feed, or basal diet plus 50 or 100 mg oregano essential oil kg(-1) for 38 days prior to slaughter. Lipid oxidation was assessed by monitoring malondialdehyde (MDA) formation in raw and cooked meat during 0, 3, 6 and 9 days of refrigerated storage, using the thiobarbituric acid (TBA) assay and third-order derivative spectrophotometry. Results showed that dietary oregano essential oil supplementation exerted antioxidative effects, the supplementation being most effective in retarding lipid oxidation in stored raw and cooked meat at the 100 mg oregano essential oil kg(-1) feed. However, dietary α-tocopheryl acetate supplementation at 200 mg kg(-1) feed displayed greater antioxidant activity than oregano treatments. Thigh muscle was more susceptible to oxidation compared to breast muscle in all treatments, although the former tissues contained α-tocopherol at markedly higher levels.