Using a large student-level dataset from a medium-sized regional comprehensive university, we measure the impact of taking an online prerequisite course on follow-up course grades. To control for self-selection into online courses, we utilize student, instructor, course, and time fixed effects augmented with an instrumental variable approach. We find that students’ grades in follow-up courses can be expected to be nearly one twelfth of a grade point lower if the prerequisite course was taken online. These results are robust to self-selection into online courses and into subsequent course enrollment.