Technical Abstract: This research aimed at developing quick cooking brown rice by investigating the effect of ultrasonic treatment at different temperatures on cooking time and quality. The medium grain brown rice was ultrasonically treated in water at temperatures of 25°C, 40°C and 55°C for 30 min and then dried by air at 25°C to its initial moisture content (11.0±0.6% w.b) before cooking. The microstructure of rice kernel surface, chemical composition and optimal cooking time of treated brown rice were determined. The pasting and thermal properties and chemical structure of flour/starch from treated brown rice were also examined. The results showed that the optimal cooking times were reduced to 37min, 35min and 33min after the treatments at 25°C, 40°C and 55°C, respectively, compared to the control of 39.6min. The ultrasonic treatment resulted in a loss in natural morphology of rice bran, allowing water to be absorbed by rice kernel easily, particularly at high treatment temperature. Even through rice flour still maintained A-pattern in the pasting properties, the crystallinity significantly increased after the treatment at 55°C. Ultrasonic treatment increased the peak, hold and final viscosities and decreased the onset temperature and peak temperature (Tp) significantly. It is concluded that ultrasonic treatment could be used for reducing cooking time of brown rice.