Despite increased attention to the preparation of teachers and the precise nature of the knowledge they need to be effective, the teacher education community currently lacks a knowledge base for teacher educators. A knowledge base for teacher education includes not only a focus on developing coherent curricula for preparing preservice teachers, but also includes attention to ways of supporting teacher educators in their work with preservice teachers. However, the field of teacher education lacks an evidence-based understanding of the practices of teacher educators, which limits the field’s ability to develop and support the individuals who are primarily responsible for the preparation of preservice teachers. This is particularly important as we use the phrase “teacher educators” to refer to individuals who teach courses for preservice teachers, which includes content experts, graduate students, education researchers, and classroom teachers who not only have different professional backgrounds, but who are often not professionally prepared for the work of teaching preservice teachers. As I will discuss in this presentation, my research focus has shifted from a focus on preservice teacher learning to a focus on understanding the nature of teacher educators’ work as they support preservice teacher learning. I will present examples of the ways in which I have studied mathematics teacher educators’ work, in particular, as well as discuss the implications for research in teacher education more broadly.