Teamwork is important when humans work together with automated agents to perform tasks requiring monitoring, coordination, and complex decision-making. While human-agent teams can bring many benefits such as higher productivity, adaptability and creativity, they may also fail for various reasons. It is important to understand the tradeoffs in teamwork. The purpose of this research is to investigate the process and outcomes of human-agent teamwork by running experiments and building quantitative simulation models. Preliminary results are discussed as well as future directions. We expect this research to deepen the under-standing of human-agent teamwork and provide recommendations for the design of teams and agents to support teamwork.