Research has shown that the underlying teaching beliefs or theories of any particular teacher have generally been considered relatively stable and static throughout his or her career. However, this study investigates how one teacher's beliefs regarding both teaching and learning were changed during a short-term study and immersion program abroad. The teacher at the focus of this research was studied over a period of 9 months using interviews and classroom lesson observations. By giving the teacher opportunities to test methodological hypotheses through actual teaching, this study proves that a short-term immersion program can change teacher beliefs and resolve some of the cognitive dissonance about effective teaching. It was found that some of the teacher's fundamental beliefs were challenged and altered, such as those on task-based teaching and learning, as well as learning outcomes. (Contains 5 tables and 2 figures.)