Teacher education in Norway has the form of a five-year, research-based program with three or four subjects studied at the master's level. The aim of the project that this study builds on was to both prepare student teachers for future work and enhance their development in schools and universities as they worked on their R&D assignments and master's theses. Teacher education relies heavily on collaboration between schools and teacher education institutions. With cultural-historical activity theory as the theoretical framework, a change laboratory (CL) became the meeting place for the participants in the study. 16 CL sessions were arranged during the four-year project. The data were collected during the last CL session. The teacher educators in university and in school sat in their respective groups, having a dialogue around the question, What have you learned during your work on the R&D assignment and the master's thesis, and what significance do you think your learning will have? The study shows that teacher educators in university and school co-constructed knowledge of a new activity related to a collaboration between university and school, and that the development work became important for both parties.