Though there is an extensive literature on materials in language teaching, little if any of it examines the relationship between materials such as textbooks and the totality of the classroom experience. The present study makes use of the concept of classroom ecology (Tudor, 2001; van Lier, 1996) to explore the interrelationships among materials and other crucial elements in an advanced ESL grammar class offered in the Intensive English Program of an American university. We focus in particular on the ways in which the textbook—Azar's (2002) Understanding and using English grammar—constituted the de facto curriculum of the course, and how it provided structure for the majority of the classroom interaction. Finally, we speculate on the relationship between the materials and language learning in this classroom. We argue that the framework of ecology, with its emphasis on affordances and emergence, provides a compelling lens through which to study the ways in which materials are actually deployed in classrooms, and how teachers and students conceive of the work being done there.