Calls for teamwork in health care are as persistent as they are hard to heed. Over the past decade, a growing number of observers, ourselves included, have called attention to the need for providers to coordinate better across specialties, shifts, departments, and even organizations (for example between primary care and urgent care facilities) to produce safe, affordable, high-quality care. Cross-boundary teamwork is particularly important when caring for patients who have chronic conditions and multiple additional diseases, increasing the need for collaboration among diverse providers. This type of teamwork is also critical in making the customized, time-sensitive care decisions required in busy emergency departments staffed around the clock by over-stretched clinicians. Prior research in health care and other industries makes clear the importance of team stability for team performance in general, yet stable teams are not always possible with chaotic 24/7 operations and heterogeneous work schedules.