To prepare students for effective workplace learning, it is necessary to have insight into the contextual characteristics that affect students' developing interest. Aiming at students to become self-regulated learners, teachers should act as mindful coaches, encouraging their students to monitor the quality of collaborative group work. A field study was conducted within the context of a Computer Supported Collaborative Learning (CSCL) project fostering self-regulated learning. Students and teachers made use of an electronic instrument that assessed and visualised students' experiences of the quality of group learning over time. 137 vocational students in commerce and business administration participated in a 6 months project requiring to work in small learning groups. A SEM model, based on self-determination theory, fitted the data quite well. Perceived autonomy, competence, and social relatedness seemed to be good predictors of students' situational interest. Qualitative interview data revealed not only the added value of process-oriented reflection and within-group discussion, but also some shortcomings concerning the effectiveness of (implementing) CSCL.