This study investigated whether the type of course materials used by instructors in postsecondary education had an impact on their teaching approach. The study focused on two approaches to teaching, teacher-focused and student-focused, and examined the use of Open Educational Resources (OER) versus commercial materials as the independent variable. The theoretical framework used to guide the study was constructivism, and the Relational 3P conceptual framework was applied to analyze the process stage of teaching. The results of the one-way MANOVA revealed that the effect of course material type on instructional approaches was statistically significant (F(2, 334) = 3.40, p = 0.034, eta[superscript 2]p = 0.02). Specifically, the null hypothesis was rejected for the conceptual change/student focused (CSSF) instructional approach (F(1, 335) = 5.72, p = 0.017, eta[superscript 2]p = 0.02). However, there was a failure to reject the null hypothesis for the transmission/teacher-focused instructional approach (ITTF) (F(1, 335) = 1.17, p = 0.281, eta[superscript 2]p = 0.003). These findings have important implications for understanding the impact of course materials on teaching approaches and student learning outcomes in postsecondary education. Instructors who reported using OER scored higher on the more robust CCSF instructional approach than those who used commercial materials. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]