This longitudinal qualitative study investigated the impact on teacher participants of using a unique laboratory approach to professional development: the Team Teaching and Learning (TTL) framework, which integrates five traits from Garet, Porter, Desimone, Birman, and Yoon's (2001) empirical research on teacher professional learning, including content knowledge, active learning, coherence, collective participant, and duration. Participants included 24 teachers in one high-poverty school district in the Northwest United States who participated in a three-week summer professional learning experience. Results indicated seemingly high implementation of professional development content, which also appeared to be sustained over the two-year time frame of the study. This pilot study of TTL contributes to literature on collaborative teacher learning and provides school leaders with numerous recommendation strategies that make implementation successful. The TTL framework is founded in empirical research and utilizes best practices for teacher and adult learning.