A primary motivation for using Open Educational Resources (OERs) is to increase access by reducing students’ financial burden. While this was a motivating factor in this study, the authors also were interested in understanding OER’s impact on student learning. Therefore, this study describes the adaption process for an OER textbook used in a junior-level undergraduate electricity course and evaluates this OER’s effectiveness to increase student access and improve learning over the baseline textbook. A quasi-experimental, non-equivalent design collected exam scores, and self-reported survey responses from n=144 students in a comparison (non-adapted OER; n=83) and treatment (adapted OER; n=61) group was used. Based on Student’s t, Kolmogorov Smirnov, and Chi-square (χ2) tests, the adapted OER was effective at improving access and learning while also saving enrolled students an average of $8,000 per year, collectively. A brief background of OER databases, materials, and methods used to develop the OER and the intellectual contribution of the newly adapted OER, and lessons learned are included in the study.