Teaching is often characterized as an isolated activity, yet opportunities for teachers to work and learn together in schools are increasing. Underlying this shift is the view that as teachers work on new practices and teaching challenges together, they will express varied perspectives, reveal different teaching styles and experiences, and stimulate reflection and professional growth. Despite strong research interest in teacher learning groups, few studies have looked at the relationship between teachers' conversations and collaboration outside the classroom and their actual classroom teaching. Drawing on data from a larger study of literacy instruction with middle-school teachers, this article describes how three teachers participated in an ongoing literacy program with a research group. Two were seventh- and eighth-grade language-arts teachers, the third was a special-education teacher who taught a substantially separate class of cognitively delayed and learning-disabled students. Case studies of each teacher draw on meeting observations, classroom observations and interviews to describe how each participated in after-school meetings, how they used the work of the group in the classroom, and how they brought teaching successes and challenges back to the group. Although each of the teachers participated actively in the teacher learning group and changed their practice, the teachers with the most advanced teaching of literacy practices did not bring that expertise into the teacher group as fully as they might have. The analysis raises questions about how teachers participate and learn and how to structure teacher groups to maximize teacher learning. (Contains 1 figure, 3 tables and 1 chart.)