STEM teacher leadership represents the intersection of two important educational foci in the U.S.: STEM education and teacher leadership. This paper set includes studies that explore a conceptual framework for STEM teacher leadership both theoretically and empirically. Within that set we will describe how the conceptual framework has evolved, as well as what we have learned about the impact of that framework on the teacher and leadership development of a group of 32 teaching fellows (TFs) and master teaching fellows (MTFs) in the Noyce-funded I-IMPACT project. Paper 1 will describe the development of the framework and initial insights concerning the internalization of key principles from it by the MTFs. Paper 2 will describe how used social network analysis has been used to examine the MTFs participation in various communities of practice. Paper 3 looks at how the EQUIP observation protocol has been utilized to examine MTF-TF mentoring interactions. Paper 4 explores how the Multifactor Leadership Questionnaire can be utilized to trace the leadership development of both the TFs and MTFs. Finally, paper 5 considers how both utilization-focused and theory-driven evaluation frameworks can be used to examine identity development and teacher leadership capacity of project participants.