As the emphasis on preventing obesity has grown, so have calls for interventions that extend beyond individual behaviors and address changes in environments and policies. Despite the need for policy action, little is known about policy approaches that are most effective at preventing obesity. The Centers for Disease Control and Prevention (CDC) and others are funding the implementation and evaluation of new obesity prevention policies, presenting a distinct opportunity to learn from these practice-based initiatives and build the body of evidence-based approaches. However, contributions from this policy activity are limited by the incomplete and inconsistent evaluation data collected on policy processes and outcomes. We present a framework developed by the CDC-funded Center of Excellence for Training and Research Translation that public health practitioners can use to evaluate policy interventions and identify the practice-based evidence needed to fill the gaps in effective policy approaches to obesity prevention.