This study compares undergraduate student exam performance of classroom and online course sections that have nearly identical instructional designs. The sections differed only in lecturing and peer discussion activities that are typical differences of classroom and online instruction. Classroom discussion activities were synchronous speech and online discussion were asynchronous text. Composite mean exam scores show a large effect size difference that is statistically significant. Results suggest that asynchronous peer-to-peer discussion is more effective than traditional classroom lecture-discussion for undergraduate students.