In this study we created an environment for peer learning, where students teach students by making oral presentations in groups about solving mathematical problems and explaining the theoretical background in mathematics, during the first year of an undergraduate engineering programme at the Norrkoping campus of the Linkoping University. In order to strengthen the students' understanding and perception of central mathematical concepts, the study was designed to take the students through five different learning experiences, "preparing" the presentation, "presenting" the mathematics, "listening" to others presenting, "discussion" by all students after the presentation and "feedback" by the teacher to the small group of students separate from the other students. We study how oral presentations work as a learning and assessment method. The study consisted of three stages. After a first run of the presentations as a learning instrument, three guidebooks with recommendations for students and teachers were developed in order to assist students as well as teachers about their role in this learning environment. Students' and teachers' views on the student presentations as learning instrument were surveyed before and after the intervention. In stage three, students were interviewed individually to ascertain the relevant success of the different learning experiences. (Contains 4 figures.)