Annual Emergency Department (ED) visits have increased 44% over the last two decades while the number of EDs nationwide has fallen by 11%. This increase in demand has led to overcrowded EDs and increased length of stay, both of which have the potential to negatively affect patient outcomes and satisfaction. The University of Virginia (UVA) ED is considering process changes to the express care treatment area, an area that mostly treats low acuity patients, in an effort to reduce length of stay. We developed a discrete-event simulation model to assess the impact of changes to the express care area, including the number of treatment beds, hours of operation, and the types of patients sent to express care. Then, we developed a regression metamodel to analyze the impact of the proposed changes. The model findings suggest the current UVA ED express care settings are near optimal among the options considered.