This study analyses the teachers’ perceptions of their capacity for designing and developing STE(A)M projects in a professional development programme (PD) conducted through a collaborative educational research project carried out between the University and the centres by the IndagaSTEAM Escuela project. Incorporating STEAM education in the classroom poses various challenges to teachers, among other aspects, associated with conceptualising, designing and applying the curricular integration of STE(A)M subjects, requiring training programs updates for this purpose. Hence, the design developed promotes applying an inquiry-based approach and adapting the integrative STE(A)M curriculum in the Primary Education classroom. Challenges and opportunities of the teachers’ involvement have been analysed as a case study undertaken longitudinally between 2019 and 2022. Data have been compiled from a varied typology (rubrics evaluation, ad hoc interviews and questionnaires, using the Likert scale), which give an account of the global perception these educators have, on the one hand, of STE(A) M education and the inquiry approach and, on the other hand, of the collaborative learning scenario from the framework used.