This experiment was performed to study the effect of dietary protein level supplemented with yeast (Saccharomyces cerevisiae) or bacteria (lactic acid) as probiotic on performance of quail birds from 7 to 49 day. Four hundred and fifty unsexed quail chicks were assigned into ten treatment groups (45 birdes/ treatment) each having three replicates (15 birdes/ replicat). Chicks of group 1 (control group) were fed the starter and finisher diets (24 and 20 % CP) that did not supplemented with probiotic. The chicks of groups 2, 3, 4 and 5 were fed the control starter and finisher diets (24 and 20% CP) supplemented with 0.5 and 1 g of either yeast or bacteria per kg feed, respectively. Chicks of group 6 were fed the starter and finisher diets (22 and 18% CP) without probiotic. The chicks of groups 7, 8, 9 and 10 were fed the control starter and finisher diets (22 and 18% CP) supplemented with 0.5 and 1 g of either yeast or bacteria per kg feed, respectively. Body weight, weight gain and feed intake were recorded. Feed conversion ratio (g, feed/ g, gain) and protein conversion ratio (g, protein/ g, gain) were calculated. At the end of the experiment carcass characteristics were measured, blood samples were taken to determine some blood protein constituents. The economic efficiency values of dietary treatments were calculated. The results revealed that, birds fed diet containing 24 and 22% crude protein diet supplemented with 1 g yeast/ kg diets during starter and grower period, respectively recorded significantly (P≤0.05) the best body weight, body gain, feed conversion ratio, protein utilization ratio and nutrients digestive compared with control diet. The inclusion of 1g yeast/ kg diets in quail diets containing 24 or 22% crude protein recorded the higher economical efficiency (expressed as % net revenue/feed cost) compared with control diet.