Current outpatient delivery systems have been problematic in their ability to effectively schedule appointments and grant patients access to care. A better appointment system has demonstrated improvement on these issues. The objective of this study is to develop a grid appointment system to further improve the scheduling flexibility by determining the minimum length of appointment slots that optimizes the total costs of patient waiting, physician idling, and overtime. This minimum length is used for the patient type requiring the least amount of treatment time such as return visit (RV), and multiplications of the minimum length are for patient types with longer treatment such as new patients (NP). The results indicated that the proposed grid system adjusts to demand changes at least 15% more cost-effective when grouping two RVs into an NP or dividing an NP into two RVs compared to the base-line scheduling approaches that build around the mean treatment time.