Teaching researchers commonly employ group-based collaborative learning approaches in Teaching of Psychology teaching activities. However, the authors know relatively little about the effectiveness of group-based activities in relation to known psychological processes associated with group dynamics. Therefore, the authors conducted a meta-analytic examination of whether learning outcomes are moderated by aspects of group process and collaborative learning. Results indicated that (a) group duration of a brief period (one to three classes) was more effective than group duration lasting more than one-half semester, (b) high levels of participant interdependence were associated with greater learning outcomes, and (c) group activities incorporating a formal group project presentation evidenced significantly less robust learning outcomes than activities that did not include a formal group presentation. Based on the findings, the authors provide teaching suggestions that reflect how group processes may impact learning effectiveness. (Contains 1 table.)