The writing-to-learn (WTL) literature is varied in how assignments are structured and implemented in the classroom, making it difficult for instructors to identify how to incorporate writing effectively. Drawing on the WTL literature, the MWrite program was established to work with STEM faculty to design, implement, and assess evidence-based WTL assignments. Herein we present a review of the WTL research generated through the MWrite program, situating our findings in a four-dimensional framework of engagement to identify how the MWrite WTL assignment design and implementation has supported students' learning. Our analysis indicates that the multi-faceted design of MWrite WTL assignments supports students' development of conceptual knowledge and disciplinary thinking. The assignments' rhetorical features (i.e., context, audience, and genre) guide how students write about content, and peer review and revision stages encourage a collaborative, knowledge building process between students and their peers.