This paper presents the results of the first test of the investment model for predicting attitudinal loyalty in service industries. Application of the investment model in the service context of casual dining restaurants has the potential to improve the understanding of the role of quality and the reasons that customers are loyal or disloyal to these restaurants. A focus on quality allows firms to improve performance and, as a result, improve customer retention. The research method in this work employs a survey data collection approach. Confirmatory factor analysis is used to test the predictive power of the investment model as it relates to quality and the associated retention of customers within the casual dining restaurant domain. The authors’ results show that service satisfaction and investment size substantially predict a customer’s loyalty to casual dining restaurants. These results provide service managers with insights into customers’ attitudes toward casual dining restaurants and extend the body of knowledge on the antecedents that predict attitudinal loyalty in a service industry. This study is the first to operationalize the investment model in the casual dining services domain as well as to examine customers’ internal and external motives and the role that quality plays in creating loyalty to a casual dining restaurant