Course-based undergraduate research experiences (CUREs) offer students opportunities to engage in critical thinking and problem solving. However, quantitating the impact of incorporating research into undergraduate courses on student learning and performance has been difficult since most CUREs lack a comparable traditional course as a control. To determine how course-based research impacts student performance, we compared summative assessments of the traditional format for our upper division immunology course (2013-2016), in which students studied known immune development and responses, to the CURE format (2017-2019), in which students studied the effects of genetic mutations on immune development and responses. Because the overall class structure remained unaltered, we were able to quantitate the impact of incorporating research on student performance. Students in the CURE format class performed significantly better on quizzes, exams, and reports. There were no significant differences in academic levels, degree programs, or grade point averages, suggesting improved performance was due to increased engagement of students in research.