Large-scale behavior change interventions, delivered through a variety of platforms – government health systems, community-based platforms, and mass media – had substantial impacts in Bangladesh, Ethiopia, and Vietnam. A body of evidence, based on A&T evaluations in these countries, now informs approaches to shaping nutrition behaviors around the world. We conclude that carefully done collaborative program evaluations that use randomized controlled trials together with other methods can support effective learning about solutions, even those that operate at scale.