Two Connecticut programs designed to support beginning teachers, the Beginning Educator Support and Training Program (BEST) and the Cooperating Teacher Program (CT), are grounded in the collaborative leadership concept. A working partnership between principals and mentor teachers shares responsibility with a state assessment team to support and evaluate new teachers. Identification of principals' supervisory roles and responsibilities to teachers and an examination of principal-teacher interaction in the collaborative process is the purpose of this study. Data were collected from indepth interviews with 15 participating educators, an expert panel discussion, and document analysis. Findings indicate that little collaborative supervision occurred, due to an imbalance of power and impaired communication based on state confidentiality requirements. However, teachers felt supported by principals, and principals demonstrated effective instructional leadership. Results suggest that the BEST and CT programs enhance opportunities for improving instructional leadership by principals and teachers. Recommendations are offered for principal training, role clarification, and school improvement. Tables summarize characteristics of interaction among supervisors, mentor teachers, and beginning teachers. (LMI)