Abstract: This study evaluated the effect of dietary supplementation of antimicrobial cold pressed oils mixture [1:1:1 of Nigella sativa, cloves and rosemary (NCR)] at levels of 0.75 and 1.5 g kg–1 diet, on growth performance, carcass traits and some microbiological aspects for growing Japanese quails. A total number of 225 growing Japanese quails one week old were used in a complete randomized design experiment with three treatments. Final live body weight was significantly (p<0.01) higher by 2.89% in quails fed diet supplemented with 1.5 g NCR oil compared to those fed the control diet. Feed intake increased statistically (p<0.01) as the level of oil mixture supplement increased. The best feed conversion of 2.87 was associated with 1.5 g oil during period 3-6 weeks of age, whilst the control group gave the best feed conversion within the whole period (1-6 weeks of age) followed by the experimental group treated with 1.5 g NCR oil. Feeding quails on a diet enriched with 1.5 g NCR oil resulted in the best carcass percentage which increased by 3.72% compared to those fed the control diet. The populations of Total Bacterial Count (TBC), coliforms and Escherichia coli in ileum, ceca and feces were fewer (p<0.05) in quails fed diet supplemented with NCR oil mixtures (1.5 g w/w) compared with the control diet. In conclusion, the dietary supplementation of antimicrobial cold pressed oils mixture by 1.5 g kg–1 showed the potential to enhance the growth performance and reduce intestinal and excreta pathogenic bacteria in quails.