The overwhelming majority of team or group composition studies are restricted to analyzing the link between team demographics and the content of specific strategic choices. We argue that in order to make progress in this domain it is now time to broaden the approach by focusing on psychological team composition and issues of effective implementation. In addition, we propose a more sophisticated theoretical and methodological approach to the use of specific team composition measures. We conducted an experimental study in order to explore the potential of addressing these major limitations of past research. Specifically, we hypothesize on and analyze the relationship between the psychological composition of management teams (in terms of their members' control perceptions) and two aspects of effective strategy implementation: meticulous planning and the configuration of consistent action patterns. We find that homogeneous 'internal' teams adapt their strategy-making behavior to the requirements of the environment, whereas homogeneous 'external' teams do not. As expected, mixed (i.e., heterogeneous) teams experienced most problems in effectively implementing their strategies. The findings provide support for the potential value of analyzing both psychological composition of decision making teams and strategy implementation issues. Furthermore, it underscores the importance of properly matching theoretical expectations and measurement methodology in multi-level research.