Self-regulated learning (SRL) can be fostered by teachers' behaviour and feedback and by the creation of suitable learning environments. This paper tackles the problem of how to develop attitudes and competences enabling teachers to act in support of their students' SRL. To this end, teachers should be aware of their own self-regulation of both learning and teaching behaviour, so as to cope flexibly with the needs of their students. This paper analyses the features and the rationale behind some of the online collaborative activities proposed to trainee teachers, in the context of a course on Educational Technology and investigates their effects in terms of SRL practice during the course. The investigation was based on the analysis of the interactions among the trainees, searching for indicators of self-regulated actions and distinguishing among SRL phases (planning, monitored execution and evaluation), SRL components (cognitive/metacognitive and emotional/motivational), and working mode (individual and social). The outcomes of the interaction analysis show that self-regulated actions were repeatedly carried out during the course, confirming the expectations of the instructional designers. The study distinguishes between the different types of SRL actions carried out by the trainees, shedding light on the relationship between tasks and effects of SRL practice.