Universitas Indonesia has implemented a Learning Management System (LMS) known as Student-Centered E-Learning Environment (SCeLE). The SCeLE facilitates collaborative learning through an online discussion forum. Collaborative learning can promote critical thinking. However, students will have difficulties contributing and understanding discussions when the discussion process is fast, lengthy and when diverse ideas arise. This could lead to uncertainty and demotivation among the students. On the other hand, teachers have difficulties in monitoring students' understanding and the discussion progress. Consequently, providing constructive feedback promptly becomes challenging. This study proposed an online collaborative summarizing feature to be integrated with the online discussion forum to facilitate the construction of a discussion summary. The tool was developed using the User-Centered Design (UCD) approach and tested using the usability evaluation. The participants (both students and lecturers) found that the usability of the developed system was good. This was indicated by the fact that more than 80% of the students and more than 80% of the lecturers were able to finish the tasks given easily. Furthermore, the SUS score exceeded the average score, meaning that students and lecturers found that the developed system had a good usability.