Resurgences of COVID-19 cases are a grave public health concern. Hence, there is an urgent need for health care systems to rapidly and systematically learn from their responses to earlier waves of COVID-19. To meet this need, this article delineates how we adapted the World Health Organization's After Action Review (AAR) framework to use within our health care system of the United States Department of Veterans Affairs. An AAR is a structured, methodical evaluation of actions taken in response to an event (e.g., recent waves of COVID-19). It delivers an actionable report regarding (i) what was expected, (ii) what actually happened, (iii) what went well, and (iv) what could have been done differently, and thus what changes are needed for future situations. We share as an example our examination of Mental Health Residential Rehabilitation and Treatment Programs in Massachusetts (a COVID-19 hotspot). Our work can be further adapted, beyond residential treatment, as a consistent framework for reviewing COVID-19 responses across multiple health care programs. This will identify both standardized and tailored preparations that the programs can make for future waves of the pandemic. Given the expected resurgences of COVID-19 cases, the time to apply AAR is now.