Open Educational Resources (OER) are online teaching and learning resources available for instructors and students to utilize at no cost to them. This case study reports on the impact of OER resources on students' academic performance in an undergraduate introductory astronomy course at a 4-year private university. As part of this study, we compared the students' performance using traditional standard textbook with the newly introduced OER resources while maintaining the same quality of instructional and learning materials. Our findings indicate that the carefully chosen OER resources could serve the need for students and instructors and help to reduce or eliminate the high textbook cost, which is often considered a barrier for many students in higher education. Finally, we discuss the student perceptions about the OER resources and how it could effectively change the higher education in years to come.