Earlier self-efficacy studies have been blamed for their methodological weakness and their mere reliance on self-report, survey, and correlational techniques for data collection. The purpose of this study; therefore, was to assess the impact of Feuerstein’s theory of mediation on EFL teachers’ sense of efficacy through direct observation rather than self-reports and to use experimental techniques to measure changes in the three key components in teachers’ self-efficacy -- efficacy in student engagement, efficacy in instructional practices, and efficacy in classroom management-- in 16beginning teachers participating in their in- service teacher development program. Intervention strategies-- modeling, rehearsal, and videotape analysis-- were implemented over a span of 15 two hour sessions. Progress was also monitored by students’ engagement in a real teaching performance followed by their self/ peer evaluation. Results of this study indicated that the participants made significant gain scores for all three components.