The antioxidant effect of oregano essential oil and vitamin E was evaluated in cooked chicken breast meat. In total, 480 broilers were randomly assigned to 6 treatments and 4 replications. Broilers were raised with a corn-soybean meal diet including either crude soybean oil or acidulated soybean oil soapstock, each supplemented with vitamin E at 10 or 100 mg or oregano essential oil at 100 mg/kg of feed. At 42 d, broilers were slaughtered and their breast meat was prepared into strips (1.5 × 10 cm) or patties (150 g). Fatty acid composition of the muscle was determined. For lipid oxidation stability, both meat strips and patties were cooked to an internal temperature of 74°C and malonaldehyde contents were assessed during 0, 3, 6, and 9 d of storage at 4°C. Each storage day had 4 replications per treatment. The meat lipid oxidative stability was estimated by content of malonaldehyde values. Results showed that feed consumption, weight gain, and feed conversion were not affected by the dietary oils or antioxidants, except for the mortality in acidulated soybean oil soapstock with the 10-mg vitamin E treatment. The fatty acid composition of the meat was similar between the 2 diets given the same antioxidant supplement. The oxidation stability of meat lipids in both types of meats showed a significant (P < 0.05) interaction between oils, antioxidants, and storage time. In the crude soybean oil oil diet, the malonaldehyde value in the 10-mg vitamin E treatment was the highest, followed by oregano essential oil, and then the 100-mg vitamin E treatment at 9 d of storage, whereas the value of oregano essential oil in the acidulated soybean oil soapstock diet was the highest, followed by the 10-mg vitamin E, and then the 100-mg vitamin E treatment during the 9 d of storage. In conclusion, the dietary oils and antioxidants used can be included in broiler diets without negative effects on their productivity. The antioxidant effect of vitamin E was higher with a higher supplementation level, regardless of the oil treatment, whereas the antioxidant effect of oregano essential oil was better in crude soybean oil than in the acidulated soybean oil soapstock diet.