The aim of this study is to define the impact of the Research Lesson Study (RLS) Model on 27 pre-secondary and secondary school teachers belonging to the Istanbul Provincial Directorate of National Education, who were involved in the “Intel Teach - Advanced Online” (ITAO) teacher training course. 27 master teachers, selected from 105 teachers as a study group, were trained in three different sessions of ITAO. The study was initiated with five-day teacher trainings in the academic years 2013-2014 and 2014- 2015 through an action research model. The 27 master teachers in this study were selected based on the criteria of their design skills, their aptitude for teamwork, and their willingness to participate in this study. Master teachers from different subjects were grouped in teams of 3, and collaborated to design their learning paths and to test the methods learned in their classrooms. At the same time, they took on the role of moderators during the ITAO teacher trainings and, in the final stage, they led teacher training during cascading seminars. The qualitative findings of the study indicated that the RLS Model enhanced the interaction among the teachers, peer learning and the perception of effectiveness. In addition, this model paved the way for the exploration of interdisciplinary teaching, innovative methods in instructional design, and the integration of ICT in classroom implementations and adult education.