Abstract: This study aimed to investigate the effects of microwave pretreatment on the quality characteristics of coarse cereals, and develop a kind of mixed coarse cereal rice with simultaneous cooking maturity. Four types of coarse cereals—mung bean, black bean, red bean, and black rice—were selected as raw materials. The optimal soaking time was determined based on water absorption rates. The influence of microwave duration on the gelatinization degree and sensory scores of the four coarse cereals was studied. Comparative analysis was conducted on the quality changes of the coarse cereals before and after pre-ripening. The proportion of the mixed coarse cereal rice was determined using sensory score as an indicator, and its digestive properties were examined. The results showed that the optimal soaking times for mung beans, black bean, red bean, and black rice were 3, 3, 8, and 2 h, respectively, while the optimal microwave times were 5, 5, 6, and 4 min, respectively. After pre-ripening, the moisture and fat content of the four coarse cereals significantly decreased, starch content significantly increased (P<0.05), and protein content remained largely unchanged (P>0.05). Pre-ripening reduced the cooking time of the coarse cereals while increasing their rehydration rate, volumetric expansion rate, and cooking loss rate. The color of the four coarse cereals was affected to varying degrees by pre-ripening. Additionally, pre-ripening significantly reduced the hardness and chewiness of the coarse cereals while significantly increasing their elasticity (P<0.05), making their texture more similar to that of cooked rice. Except for mung beans, the odor response values of black beans, red beans, and black rice increased after pre-ripening. With the exception of black beans, the viscosity, breakdown, and setback values of mung bean, red bean, and black rice significantly decreased after pre-ripening, while their gelatinization temperature significantly increased (P<0.05). The optimal formulation for the mixed coarse cereal rice was determined as follows: Pre-ripened mung bean:pre-ripened black bean:pre-ripened red bean:pre-ripened black rice:regular rice=15:10:5:21:49. Compared with rice, this mixed coarse cereal rice had a higher content of slow digestible starch and resistant starch, which were 45.16% and 26.45% respectively, and its estimated glycemic index (GI) was 64.61, which was a medium GI food. These findings provide data support for the application of microwave precooking in coarse cereal processing and contribute to the advancement of the coarse cereal processing industry.