Findings from a meta-analysis of meta-analyses of 14 different types of preservice student and beginning teacher preparation practices are described. The research synthesis included 118 meta-analyses and 12 other research studies of preservice practices-preservice student and beginning teacher outcomes. The research reports included between 5000 and 6000 studies and an estimated 2.5 to 3 million study participants. The outcomes included two different teacher quality measures and two different preservice student and beginning teacher measures. Mean difference effect sizes, confidence intervals for the average effect sizes, and generalized patterns of results were used to identify very high impact, high impact, medium impact, low impact, and no impact preservice practices. Results showed that clinically rich field experiences (extended and limited student teaching), learning experiences that included multiple opportunities for deliberate practice, faculty and school-based coaching, clinical supervision and performance feedback, different types of experiences and opportunities to learn to teach, course-based experiential learning experiences, and cooperative learning opportunities stood out as especially important practices that were related to optimal preservice and beginning teacher outcomes. The patterns of results are consistent with a practice-based approach to teacher preparation where the focus of preservice and beginning teacher education is the learning experiences and opportunities to learn and use optimal effective teaching practices.