Multi-parameter extrusion cooking conditions for the extrusion of composite flours of rice and soybean were modeled using response surface methodology (RSM). A five-level-three-factors central composite rotatable design (CCRD) was employed to optimize three process variables including barrel temperature (BRT)(X 1 ), feed moisture (FMC)(X 2 ) and feed soybean composition (FSC)(X 3 ) for the achievement of satisfactory hydration characteristics and proximate composition. The fitted polynomial models indicated significant coefficients, satisfactory coefficients of determination (R 2 and R 2 adjusted ) and non-significant lack-of-fit test. Optimum X 1 , X 2 and X 3 were 120˚C, 20%, and 23% for rice-soybean based extrudates. At these optimum combinations, optimum responses were 97.10% for dispersibility, 6.11 water absorption index and 8.42 water solubility index, while proximate composition of 1.02% moisture content, 3.62% lipid, 26.26% protein, 0.48% ash content, 2.14% fibre, 70.13% and 412.14 kcal/100g of energy were obtained. Under the optimized conditions, the responses are well matched with the predicted values and therefore the models could be used to predict the extrusion system in its natural state.