This article shares the results from a quasi-experimental mixed-methods study of a promising transition-focused professional development approach. The 12-week team-based intervention resulted in positive outcomes among intervention group participants' knowledge and capacities. The intervention group exhibited statistically significant changes in knowledge of transition assessment practices as well as in using various types of age-appropriate transition assessments and implementing effective practices associated with a comprehensive transition assessment process. At the program level, findings indicated team-level indicators showed statistically significant improvements. The study demonstrated teams who received the intervention were more likely to attain a program-level goal, which was substantially greater than the comparison teams. Implications for future research and practice are shared.