Teacher research (practitioner inquiry) is an effective form of professional development for middle level teachers. Through teacher research, classroom teachers develop the skills needed to demonstrate mastery of the performance standards for middle level master teacher candidates. Using well-established research methods, middle level educators conduct classroom inquiry projects to investigate their teaching and their students' experiences and learning. This article explains the work of 4th to 9th grade teacher researchers who investigated: (a) new teaching methods or curriculum, (b) approaches to teaching that allow for teachers to meet the needs of all learners, (c) transitions for young adolescents or teachers, and (d) experiences that support young adolescents' thinking and development. In order to describe the teacher research model, two middle level educators share their experiences of conducting research in their 5th grade classrooms. Throughout the article, the authors draw connections between middle level teachers' research experiences, student and teacher learning.