STEM transformation has been a longstanding goal for higher education institutions who not only wish to maintain global economic competitiveness but most recently have also aimed efforts at achieving STEM equity. While researchers have typically looked to students' and faculty's experiences for answers, STEM program directors possess great insight from working closely with students in both faculty and administrative roles. This study explores the views of 45 STEM program directors at 10 institutions across the U.S. that had high STEM bachelor's degree-completion rates relative to similarly resourced institutions. We document the lessons and strategies that STEM program directors have used to broaden institutional impact, including demonstrating their program's efficacy through assessments and evaluations, coordinating, and streamlining efforts to ensure program efficiency and longevity, incentivizing support for labor, and consolidating support from institutional leaders. We also disentangle the roles STEM program directors play as grassroots leaders or institutional agents, distinguishing them by their authority and decision-making power and by whether they work to transform the institution to better serve students or to transform students' behaviors to adapt to the institution. Our findings provide avenues to leverage STEM program directors' efforts in order to move toward STEM education transformation in higher education.