Rice bran was used to increase the nutritional value of Indonesian people, especially dietary fiber, in the production of ready-to-eat cereal flakes. This research was aimed to develop optimum formula of ready-to-eat cereal flakes product by the application of rice flour, rice bran, and glutinous rice flour using response surface methodology (RSM). The experimental design with three variables (rice flour, rice bran, and glutinous rice flour) and five levels each variable (-1.682, -1, 0, 1, and 1.682) has been employed. Twenty treatments included six replications at the center point were analyzed to determine the most preferred ready-to-eat flakes product by response function of sensory acceptance. From nine combinations of toasting temperature and time, the best combination (175 °C for 7 minutes) was used in the processing of ready-to-eat cereal flakes due to toasting was considered as the important processing step that could affect the attributes of finish product. The optimum ready-to-eat cereal flakes was obtained from 61.59% rice flour, 25,00% rice bran, and 13.41% glutinous rice flour with the average values of sensory evaluation as normal to slightly like. From this formulation, the amount of dietary fiber was 2.25-2.82 grams in single serving size (28-35 grams) of breakfast cereal. In other word, this product could be claimed as "good source" of dietary fiber.