Group projects are part of the core educational experience in higher education, but many students report bad experiences. Group problems may undermine learning and cause stress and frustration. This may be prevented by monitoring and supporting groups, but this is often not feasible for teachers, who lack time and resources. This research aims to find a method for early identification of group work problems via computersupported assessment. First, interviews and focus groups provided insights into the most common group problems and which visual features students preferred in a peer assessment. Next, two assessment versions were created: a simple, time-efficient version, and a more engaging, interactive one. We also created an initial version of E-Mate, a virtual agent that provides initial feedback on the assessment. These were tested in a field study. Most students reported a positive experience with the peer assessment, regardless of the visualization used. Teachers were also positive about its usefulness. The research also supports the use of five attributes to assess group collaboration.