<p>Applied behavior analysis is grounded in data-based decision-making and evidence-based practice (EBP). EBP is increasingly reliant on evidence syntheses (i.e., the combining of findings from multiple research studies to inform on a particular topic). Within this context, outcome heterogeneity is defined as variability in the outcome measures employed across research studies evaluating a particular intervention, including what is measured, how, and when. Outcome heterogeneity has been identified as a substantive barrier to evidence synthesis across health and social care, with direct consequences for clinical guideline development and policy. This article draws on examples from behavior-analytic and adjacent research to argue that outcome heterogeneity represents a methodological challenge for behavior analysis. A Core Outcome Set (COS) is a consensus-based, standardized set of outcomes that should be measured and reported as a minimum when evaluating a particular intervention. COS have been developed across a range of health behavior change interventions (e.g., for sedentary behavior, behavioral weight management, self-management of diabetes) as a structured response to the challenge of outcome heterogeneity. This article proposes increased engagement with the broader movement toward COS and argues that behavior analysis offers methodological resources not currently included in COS frameworks. Engagement with COS infrastructure should be approached with critical consideration, incorporating reflection on both its potential risks and benefits, as well as its alignment with the principles and practices of the field of behavior analysis. Risks of engagement, including the potential marginalization of idiographic measurement and inductive experiment techniques, are identified and mitigations proposed.</p>