The following articles show the benefits of OER (in order of recency):

Watson et al. (2023) for AAC&U and ISKME: Link to PDF of Leveraging Open Educational Resources ot Advance Diversity, Equity, and Inclusion
Crossfield and Ryan (2022) for Yavapai College: Link to PDF of White Paper: Improving Student Success Through the Use of Open Educational Resources
Hilton (2020): Link to Springer page for Open Educational Resources, Student Efficacy, and User Perceptions: A Synthesis of Research Published between 2015 and 2018
Neu-Stephens (2020) dissertation: Link to PDF of Open Educational Resources and Enrollment Intensity in One Southern California Community College
Wakim and Arteaga (2020): Link to page on How We Saved Students $2 Million in 5 Years
Clinton and Khan (2019) on AERA Open page for Sage Journals: Link to AERA Open page for Efficacy of Open Textbook Adoption on Learning Performance and Course Withdrawal Rates: A Meta-Analysis
Colvard et al.'s (2018): Link to PDF of The Impact Open Educational Resources on Various Student Success Metrics
Community College Consortium for OER (CCCOER; nd): Link to page on the California ZTC Degree
Hilton (2016): Video summary