The aim of this study was to evaluate the effect of oregano essential oil (OEO) and capsicum oleoresin extract (CAO) supplementation on lamb slaughter  characteristics, meat quality, and fatty acid composition. In the study, 18 male and 18 female lambs were divided into three equal groups for a 56- day  feeding period. The first group was fed the control diet, while the other groups were fed a control diet containing either 300 mg OEO/kg or 300 mg  CAO/kg of diet. Feeding OEO or CAO had no effect on the slaughter and carcass quality of the fattening lambs. However, when compared to the female  lambs, the male lambs were found to have higher slaughter weights, hot and cold carcass weights, and dressing percentage, while having lower back fat  thickness. In addition, OEO substantially increased the intramuscular fat. Dry matter, protein, pH24, meat colour (L*, a*, and b*), drip loss, and cooking  loss were not affected by dietary treatment or sex. The addition of OEO or CAO to the diets did not change the meat lipid oxidation or sensory quality  characteristics at different storage times. However, meat from the female lambs was found to have thiobarbituric acid reactive substances (TBARS) values  lower than that of the meat from the male lambs after 2 d and 4 d of storage. However, the female lamb meat was more preferred in terms of flavour and  general acceptance. The ΣMUFA, ΣPUFA, ΣUFA, Σn-6, Σn-3, and Σn-6/Σn-3 contents of the lamb meat were not affected by the dietary treatment. As a  result, the inclusion of 300 mg of oregano essential oil/kg of DM in lamb diets is considered appropriate because of its significant contributions to the fat  composition of lamb meat.