Antibiotics have been extensively used in human and veterinary medicine. However, antibiotic residues have been found in poultry meat and egg and the consumption of poultry products containing antibiotic residues is resulted in antibiotic resistance and is harmful for human health. Thus, the utilization of growth promoter antibiotics has been banned in the European Union since 2006. Currently, there is considerable interest in replacing natural alternatives to antibiotics for poultry production. One of these alternatives is phytogenic plants [1]. Oregano with the scientific name Mentha longifolia is a medicinal plant belongs to Laminaceae family and is used for medical and culinary purposes. Oregano oil is derived from the plant leaves and is used in the industry because of its high antioxidant capacity. Thymol and Carvacrol are the two main Phenolic compounds in oregano essential oil which have antioxidant and antimicrobial properties [2]. It has been reported that the use of dietary oregano essential oil supplementation resulted to significant increase (P<0.05) in broilers breast and thigh meat antioxidant capacity compared to control group [1, 2]. In the current study, a total of 480 one-day old Ross 308 broiler chicken were randomly assigned to 6 treatments and 5 replicates of 16 birds in each. The experimental treatments were control (with no feed additive), 0.02% Virginiamycin as growth promoter antibiotic, and 0.25%, 0.50%, 0.75% and 1.0% oregano powder. At the end of experimental period (42 day of age), two birds from each cage with the closest body weight to the cage mean weight were selected and slaughtered after recording their live body weights and their carcass, breast, thigh, liver, and abdominal fat weights were measured in proportion to live body weight. The data were analyzed in a completely randomized design using the GLM procedure of SAS. Comparison of means was conducted by Duncan's multiple range test. The results of this study showed that the e
