Preparing classroom teachers to teach English Learner (EL) students continues to challenge teacher educators. This article argues for EL teaching work to be situated within theories of professional learning that focus on developing teachers who can flexibly and innovatively integrate EL instructional practice into content area teaching. We propose a framework of adaptive expertise that highlights scaffolding instructional practice while simultaneously creating opportunities for preservice teachers to collectively engage with problems of practice and critical reflection in real time in classrooms. Using data from a qualitative study involving a practice-based design--the studio day--in teacher education, we illustrate key elements of the framework. We examine the potential of studio days to help preservice teachers build integrated knowledge about rigorous mathematics and language instruction. Framing the preparation of classroom teachers to teach EL students within theories of adaptive expertise may inform teacher education pedagogies and contexts for teacher learning.