The practicum is a central dimension of preschool teacher education. Learn how to teach is a complex process which includes periods of observation, experimentation, reflection, evaluation, planning in context of real practices, providing opportunities for student teachers understand the various dimensions of teaching and apply the knowledge acquired within the theoretical courses. The importance and meaningfulness of practice periods for students teachers' professional learning has been widely acknowledged, and the literature highlights that the expert guidance, supervision is an essential component of student teachers professional development. This study aims to describe and analyze the supervision process that occurs during the practicum of preschool education master programs in Portugal. The objectives of the study are: i) to characterize the cooperative processes of professional development experienced by student teachers during the practicum; ii) identify the strengths and weaknesses of supervision processes analyzed; iii) identify guiding, coaching, and mentoring procedures that promote quality experiences during the practicum. The methodology used is qualitative, and data is collected through semi-structured interviews to university supervisors, cooperative teachers and student teachers. The participants are 6 university supervisors, 6 cooperative teachers and 6 student teachers, from two Portuguese higher educational institutions. To ensure confidentiality no information is disclosed without participants' consent and the interviews are transcribed and send to the participants for a final revision. Data point out: the key role of university supervisors and cooperative teachers to support students to make the liaison theory and practice for the development of an early childhood curriculum developmental and culturally appropriated; the importance of mentoring within the supervision process to promote the development of reflective thinking and professional development; the need of more training in supervision and mentoring for cooperative teachers and, occasionally, for university supervisors.