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.