Collaborative learning has important group-level benefits, yet most studies in higher education only focus on individual benefits of collaborative learning experiences. This study extends these insights by testing a model in which teamwork quality mediates the impact of several compositional differences (gender, nationality and teamwork expertise diversity, as well as need for cognition disparity) on groups' cognitive complexity in a sample of 159 student groups. The results support the mediating role of teamwork quality, and have important practical implications for the design of student groups in higher education. (Contains 1 figure and 2 tables.)