This study has investigated the use of an open guided inquiry laboratory course in which a group of pre-service teachers planned and implemented practical work for school purposes. The results show that peer discussions about content and instructional decisions within active designing teaching sequences have enabled the participants to become aware of several aspects of a physics teacher’s teacher knowledge. Furthermore, the pre-service teachers who participated in this project suggested that they had learnt subject matter knowledge during the Course of Laboratory Practice for Physics Teachers (CLP). In light of the results, the authors would warmly suggest including the early use of the open guided inquiry laboratory, as part of the bachelor degree studies, for preservice physics teachers.