Randomized controlled trials (RCTs) in education are common as the design allows for an unbiased estimate of the overall impact of a program. As more RCTs are completed, researchers are also noting that an overall average impact may mask substantial variation across sites or groups of individuals. Mixed methods can provide insight and help in unpacking some of the reasons for these variations in impact. This article contributes to the field of mixed methods research by integrating mixed methods into a recently developed conceptual framework for understanding variations in impact. We model the use of this approach within the context of an RCT for online courses that found differences in impact across courses.