Unequal participation poses a challenge to collaborative learning because it reduces opportunities for fruitful collaboration among learners and affects learners' satisfaction. Social group awareness tools can display information on the distribution of participation and thus encourage groups to regulate the distribution of participation. However, some groups might require additional explicit support to leverage the information from such a tool. Therefore, this study investigated the effect of combining a group awareness tool and adaptive collaboration prompts on the distribution of participation during web-based collaboration. In this field experiment, students in a university level online course collaborated twice for two-weeks (16 groups in the first task; 13 groups in the second task) and either received only a group awareness tool, a combination of a group awareness tool and adaptive collaboration prompts, or no additional support. Our results showed that students were more satisfied when the participation in their group was more evenly distributed. However, we only found tentative support that the collaboration support helped groups achieve equal participation. Students reported rarely using the support for shared regulation of participation. Sequence alignment and clustering of action sequences revealed that groups who initiated the collaboration early, coordinated before solving the problem and interacted continuously tended to achieve an equal distribution of participation and were more satisfied with the collaboration. Against the background of our results, we identify potential ways to improve group awareness tools for supporting groups in their regulation of participation, and discuss the premise of equal participation during collaborative learning.