Cost of quail feed formulations can be reduced substantially by using cheap cereal by-products such as rice bran (RB) at higher levels. The objective of this study was to determine the maximum inclusion levels of dietary RB with or without exogenous phytase, for laying Japanese quail. In a completely randomized design with a 3 x 2 factorial arrangement, 108 quails in 36 cages received six experimental diets ad libitum from 8 to 15 week. Experimental factors were three dietary RB inclusion levels (20, 30 and 40%) and two phytase levels (0 and 1000 FTU/kg). The level of dietary RB, phytase supplementation and their interaction had no significant effects on live weight or feed intake. The total egg production of the quail fed 40% RB was significantly lower than that of quail fed 20 and 30% RB. Egg laying rate of the quail fed 40% RB was significantly lower than those of the quail fed 20 or 30% RB from 6 th week onwards. By eighth week, 30% RB resulted in significantly lower egg laying rate compared to the quail fed 20% RB. Feed conversion ratio (FCR) of the quail fed 40% RB was significantly higher than those of 20 or 30 % RB fed. Adverse effects of phytate in 30 or 40% RB on egg number, egg mass and FCR were not mitigated by the supplemental phytase. It is concluded that inclusion of more than 20% RB in the diets of laying Japanese quail reduces the production performances.