Abstract: This study intends to integrate IPGA with the DEMATEL model in order to determine food quality core factors demanding restaurants’ most urgent improvement, as well as the highest effect for resource investment. It is hoped that such information can be provided as reference for casual-dining restaurants to develop food quality improvement and resource reallocation strategies under limited resources. 562 valid questionnaires were returned in Taipei City. The results showed that, from the perspective of customers, casual-dining restaurants should give priority to improving the quality dimensions of “hygiene” and “cooking.” Among various quality dimensions, experts suggested that “cooking” is the core factor with the highest effect of resource investment affecting food quality, such as visual appeal, taste, and hygiene. Moreover, this study further analyzed and found that a total of 15 quality items are located in the area of “Concentrate here”.