Many studies in the group decision support system (GDSS) literature have reported on the behavior and performance of ad hoc groups meeting for the first, and, in fact, the only time. Such one‐time studies of groups may not represent their longer term behavior and performance accurately. Adaptive Structuration Theory (AST) conceives of technology use as a social practice that emerges over time. AST suggests that meeting outcomes reflect the extent to which structures offered by the technology (such as GDSS tool sequences, meeting agenda, etc.)are faithfully appropriatedby the group. Such faithful appropriation, however, takes time. This article explicitly recognizes the relevance of this appropriation process and reports on a lab study that examined the impact of computer support on group performance over time. In general, results showed that the performance of computer‐supported groups improved over time, whereas the performance of non‐computer‐supported groups stayed the same or declined. The number of alternatives generated by computer‐supported groups increased considerably as they became more proficient in incorporating the technology into group processes. However, the quality of decisions made by computer‐supported groups began to increase slightly, only during the last session. Both these findings suggest that AST is, in fact, a viable theory for studying group behavior and performance over time. Results from this study also point out the need for conducting more longitudinal studies of group processes in the future.