As a contribution to the efforts to understand the influence of peer presence on self-regulated learning, this paper studies students' reaction to a project-based activity, the final product of which was a scientific communication to peers. In this activity, "peer lecturing," the students formulate a question on a topic linked to the course, search scientific information in order to answer the question, and teach the result of their investigations to their class in the form of a whole-class communication. The paper draws on the qualitative analysis of 23 interviews of first-year student teachers involved in "peer lecturing" in the framework of an introductory zoology course. In this study, the expressed gains in self-regulated learning described by the students are compared to the gains reported in the literature in other project-based methods and in peer teaching. Original gains in motivation ("social goals"), cognitive processes and self-regulation, are highlighted, while stressing differences between student types. Further development of the method is suggested.