This study aims to examine the processes experienced during the interaction between teacher leaders and their peers. Applying the grounded theory, we present a theoretical model that describes this interactive process in a month-long professional development (PD) program designed for teachers. As a part of the PD program, a total of 150 teachers were tasked with preparing lesson plans in accordance with the principles of Understanding by Design (UbD) and seven teacher leaders, trained and appointed by the researchers, were assigned to guide them. The findings yielded five categories: orientation, improvement, collaboration, communication, and feelings, and a main category, facilitation. It was concluded that the interactions underscore fostering teacher development by promoting professional growth and through structured learning communities, teacher collaboration help promoting educational outcomes as well as student outcomes.