We conducted research within a program serving future mathematics and science teachers. Groups of teachers worked primarily online in an asynchronous discussion environment on a 6-week task in which they applied learning-science ideas acquired from an educational psychology course to design interdisciplinary instructional units. We employed an adapted coding system to determine that group leadership was highly distributed among participants. We illustrated that leadership emerged through different forms of participation described in this paper and that, in some cases, individuals specialized in specific leadership roles within groups. Findings helped validate the theoretical concept of group cognition and led us to suggest an approach to online asynchronous learning for college students that depends more on students' emergent leadership skills than on prescriptive assignment or scripting of participant roles.