Most research and practice in teacher in-service learning focuses on formal professional development activities. This article calls for paying greater attention to the informal conversations that are embedded in teachers' day-to-day work and through which they learn from one another what it means to be a teacher and how to perform their duties. The authors build on theory and research in teacher on-the-job discourse and learning in order to (a) argue that, as a field, we need to pay more focused and systematic attention to teacher on-the-job discourse; (b) offer a coherent conceptual framework for "pedagogically productive" teacher talk; and (c) highlight key research directions and challenges in investigating this and related phenomena.