Objective: The aim of this study was to investigate the antioxidant status of post-weaned Menemen breed lambs fed with oregano (Oregano Onites L.) essential oil or hot pepper extract (capsicum oleoresin) supplemented feeds. Material and Methods: A total number of 36 post-weaned menemen breeds lambs at the age of eight weeks were divided into three groups as will be 6 females and 6 males in each randomly by control, oregano and pepper. During the experiment, all groups had access to fresh water and feed ad libitum, and the lambs were fed with a similar lamb grower feed for 56 days. Unlike the control group, 300 mg/kg of oregano essential oil or capsicum oleoresin extract were added to the feeds of the oregano and pepper groups. The experiment was maintained for 56 days. Lambs were fed lamb grower feed and fresh water was available ad-libitium during the experiment. At the end of the experiment, 6 female and 6 male lambs from each group were slaughtered in a commercial slaughterhouse and 2.5 cm thick tissue samples were taken from the longissimus dorsi muscle on the left half of each carcass to be used in the analysis. Results: It was determined that the malondialdehyde (MDA) level of the control group was higher, but the glutathione peroxidase (GPx) level was lower than the treatment groups (P<0.05). At the end of theexperiment the oxidative stress indices (OSI) of the control, thyme and pepper groups differed significantly (P<0.05), and the OSI values of the treatment groups were calculated as 0.698, 0.566 and 0.494 AU, respectively. Conclusion: Dietary supplementation of oregano essential oil or hot pepper extract had lower the total oxidant level (TOS) and OSI values, but significantly higher the total antioxidant level (TAS) in lambs (P<0.05). Results of this study indicated that both antioxidants have the potential to prevent oxidative stress in lambs, but the antioxidant capacity of hot pepper extract is higher than the same amount of oregano essential oil.