To increase the number of students who read the text before class and to promote student interaction centering on text material, I developed an online discussion assignment as a required component of a cognitive psychology course. Across 2 studies, this assignment had a limited effect on examination performance, but students completing online discussions were more likely to read the textbook in advance of class and reported reading it more carefully, particularly late in the semester. Students completing online discussions also reported understanding lectures better and feeling more prepared for exams immediately after lecture than classmates. Together, results support previous studies that suggest online discussions can be an effective tool in undergraduate psychology courses. (Contains 2 tables and 2 notes.)