We look at group work from a self-determination theory perspective and argue that internalized motivation is the best condition for productive collaboration. A perceived sense of autonomy plays an important role herein. This autonomy is determined by the characteristics of the task and the openness and acceptance of the group. Group dysfunction, or the fear of it, impedes autonomy, even if the task context is fully autonomy supportive. Means of uncovering the functioning of group members could reduce dysfunction or lower the fear of it. Using a full scale intrinsic motivation inventory, we measured the impact of group self-evaluation on the quality of motivation over a 4-year period with a total of 355 participants in a collaborative learning project in high schools (K11). We show that, compared to the control population, students exhibit a much more internalized motivation profile, with effect sizes in the range of medium to large for the different parameters. We conclude that group self-evaluation primes students for autonomous motivation. We suggest that the procedure should be applied systematically in substantial collaborative projects.