Following the argument that an explicit focus on teacher thinking is an important outcome for professional development (Capps, Crawford, & Costas, 2012; Desimone, 2009), the research presented here examines the impact of one form of professional development, Research Experiences for Teachers (RETs), has in shaping teachers' beliefs and affect related to inquiry in the classroom. By examining two distinct forms of RETs, this study incorporates 5 years of data collected from more than 100 RET participants, which include elementary, middle, and high school teachers. Evidence was drawn from analysis of multiple instruments measuring science teachers' self-efficacy (STEBI), pedagogical discontentment (STPD), teachers' beliefs about teaching and learning (TBI), and Contextual Beliefs about Teaching Science (CBATS). The results indicate that both RET programs were successful in shaping teachers' beliefs and affect--particularly in decreasing pedagogical discontentment and enhancing beliefs about reform. However, the RET program that focused mainly on teacher practice was more successful in shaping teachers' beliefs and was the only program to show an influence on teachers' practice.