In this study, the effects of oregano essential oil, on performance, some blood parameters, the antioxidant metabolism such as lipid oxidation (LPO) and glutathione (GSH) levels with superoxide dismutase (SOD) and catalase (CAT) enzyme activities in the liver and the Musculus longissimus dorsi (meat) tissue were investigated. The study consisted of three groups; the control group fed a basal ration, the OEO1 group fed a basal ration added 200 mg/kg Orego-Stim and the OEO2 group fed a basal lamb ration added 400 mg/kg Orego-Stim. The groups did not differ for performance parameters. In groups control and OEO2, serum calcium and potassium levels were significantly higher than the group of OEO1 (P<0.05). However, the serum magnesium level were significantly higher in OEO1 group (P<0.05). While there are no meaningful changes on superoxide dismutase activity, LPO and GSH rates with CAT activity had significant changes in liver tissue (P<0.05). LPO and GSH levels with SOD and CAT enzyme activities were significantly affected in M. longissimus dorsi tissue (P<0.05). As a result, while oregano essential oil did not affect the performance parameters and lipid profile, it significantly affected the antioxidant metabolism in meat and liver tissues.