This study investigated the practice of an expert reading coach as she provided lesson observation and feedback to an experienced kindergarten teacher. Data sources for the study included three cycles of observation of coaching sessions and guided reading instruction, as well as interviews. The report describes (a) the coach's modeling of pedagogical reasoning for the teacher and the co-constructed nature of the coaching session interaction, and (b) specific ways in which the coach expanded her understanding of learning to teach and learning to coach. The study concluded that the technical aspects of lesson observation and feedback require many areas of expertise, developed through time spent coaching, training and reflection, and the coach's maintenance of an expert stance within coaching relationships. (Contains 2 tables and 1 figure.)