Framed by sociocultural learning perspectives, this study examines whether embedded learning opportunities for teachers are more supportive of reflective practice than traditional professional development. All schools in this study implemented a comprehensive school reform program. The designs of the programs introduced embedded learning opportunities for teachers by adding teacher leadership positions and encouraging various forms of teacher collaboration. The results indicate that these two kinds of embedded learning opportunities are positively and strongly associated with teacher reflection, and the effects of these variables were twice the size of the effect of traditional professional development. Implications and limitations of the results are discussed.