In this work the surface response method was applied for optimizing the extrusion of a mixture of oat meal and hull corn containing soluble and insoluble dietary fiber in concentrations of 0.29% and 34.1% in hull corn, and 7.8% and 34.1% in oat meal. Hull corn showed higher water absorption capacity measured as grams of absorbed water by grams of died solid. The hydrating capacity was fitted to a quadratic model. The optimum conditions at a stationary point, using the canonical analysis, for maximizing the hydration capacity were: temperature of 128.8°C, humidity of 28.8% and 33.3% of hull corn content. The results show that the humidity and the hull corn content are the most influential variables on the extruded product properties.