In this paper, we describe a procedure to promote active participation in online courses by supporting students in performing the role of an e-Tutor during group activities. A case study, conducted to explore the procedural effects both on students' interactions and on their perceptions about the role, is discussed. Eighteen university students (67% female, mean Age = 23 years) took part in online collaborative learning activities as part of a 15-week blended learning course. Twelve participants took turns in covering the role of e-Tutor. Findings were based on a mixed methods analysis of 7105 contributions posted online by the 18 students. An analysis of e-Tutor self-assessment forms was also considered. Results indicated that utilising peer-based e-Tutors promoted substantial active participation in online discussions. Moreover, students performing the role of e-Tutor adopted a supportive, collaborative and educational style, which was maintained even after their turn as e-Tutor had ended.