The paper presents research from a Danish large-scale and collaborative initiative for systematically developing teacher education 'Teacher education as a laboratory for developing excellent teaching and education' (LULAB). Framed by this initiative, local teacher educators and student teachers are, in collaboration with teachers and students from partner-schools, experimenting with developing, analyzing, and sharing teaching approaches in teacher education. Hence, LULAB is an institutional strategic top-down initiative aimed to support the development of professional skills among student teachers and teacher educators, with supportive leadership for bottom-up changes from the microlevel projects. Inspired by design-based research, the findings are used iteratively to inform the organization of LULAB. Data are collected following a sequential mixed methods strategy, with questionnaires and multiple qualitative data. Findings from the first year of the LULAB initiative indicate a growing awareness among teacher educators about the co-developing role of student teachers being something distinctive for LULAB. Both teacher educators and student teachers emphasize their perceived professional outcomes. The student teachers refer in particular to insights from being invited into the machine room of teacher education and inspiration for their future work as teachers. However, there are also challenges involved in developing a culture of inquiry, and possibilities for support from the leadership looking forward are discussed.