Service members experience a variety of harmful behaviors that can affect their overall health and quality of life and can be detrimental to force readiness. These behaviors can include instances of service members harming others through sexual assault, harassment (e.g., sexual, bullying, hazing, reprisal, retaliation), domestic abuse, or child abuse and harming themselves through substance misuse and attempting or dying by suicide (collectively called harmful behaviors). While response and treatment are vital services to address these harms, a robust prevention system is also needed. On February 26, 2021, the Secretary of Defense tasked the U.S. Department of Defense (DoD) with developing a standardized method to conduct on-site installation evaluations (OSIEs) of harm prevention capabilities that can be paired with the improved command climate assessment process to identify and further assess installations on the basis of risk and protective factors for sexual assault, harassment, domestic violence, and suicide. DoD is implementing the OSIE biannually with select installations around the world to assess the presence of military organizational capabilities for robust prevention.In this report, we describe how the OSIE methods were developed and what we learned about the utility of those methods. This report also describes improvements to the methods that were made after initial use. It should be noted that these methods only pertain to the prevention capabilities portion of the evaluation; DoD also collected information regarding compliance with various policies during the OSIE (DoD, 2022).The findings of this report will contribute to the emerging evidence base on how to assess organizational capabilities and will be useful for professionals responsible for addressing multiple harmful behaviors in the military, for commanders, for other senior-level military leaders, and for policymakers interested in improving the quality of efforts to prevent military service members from harming themselves and others.The research reported here was completed in November 2022 and underwent security review with the sponsor and the Defense Office of Prepublication and Security Review before public release.