The Bay View Alliance (BVA; https://bayviewalliance.org/) is a network of research universities working together to support and sustain the widespread adoption of instructional methods that lead to better student learning. The BVA's research action cluster on collaborative course transformation sought and received funding from the National Science Foundation for an initiative that embeds discipline-based educational experts in science, technology, engineering, and mathematics (STEM) departments to help facilitate such change. This initiative, Transforming Education, Stimulating Teaching and Learning Excellence (TRESTLE; https://trestlenetwork.ku.edu/), has been documenting the work of seven partner institutions. The focus of the research was mainly on change in departmental cultures of teaching as a condition for ongoing improvement in undergraduates' learning experience and success. These case studies took place from 2013 through 2020 in four departments: geoscience at the University of British Columbia (UBC), the undergraduate biology program at the University of Kansas (KU), physics at Queen's University in Canada, and computer science at Indiana University Bloomington (IUB). This article describes the context for TRESTLE's work, the different models of embedded expertise deployed by each department, and what they accomplished. It offers two crosscutting lessons and conclude with reflections on how such work can be sustained and built on.