This study explored an undergraduate education initiative developed by the Association of American Universities (AAU) to improve the quality of undergraduate teaching and learning in science, technology, engineering, and mathematics (STEM) fields at its member institutions. The study relied on interviews, documents, and observations to examine strategies that have been successful in scaling and sustaining changes arising from the AAU STEM Initiative. The project explored two major questions: (1) How does the AAU Initiative achieve scale in reform of undergraduate STEM teaching and learning?; and (2) What is the role of a national association in undergraduate STEM reform and what approaches are perceived to have the most impact in achieving scale?