This research aimed to investigate and compare teachers‘ conceptualizations of their students‘ and their own outcomes of our earlySTEM program at the K4 level in two distinct roles: practitioners only and practitioners and program developers jointly. The study group included 66 teachers, 26 of whom had actively contributed to the development of the earlySTEM program. Teachers in both roles were supported by teacher guides, student books and workshops throughout the 8-month long academic year. Data was collected at the end of the academic year through an open-ended survey. The program developer teachers identified more student outcomes under more diverse categories while the practitioner teachers mainly concentrated on cognitive outcomes and limited their conceptualizations to the national curriculum. In addition, the program developer teachers valued their involvement in the program development process and expressed more diverse professional outcomes referring to different types of teacher knowledge.