This article examines the underresearched classroom context of co-teaching. The study analyzes classroom interactions wherein two teachers-one American and one Korean-concurrently use English and Korean to carry out content-based lessons. Of analytic focus is the co-teacher's entry into the second turn position of initiation-response-feedback (IRF) sequences and the actions that the teacher deploys in these turns. The sequences exhibit a distinct interactional structure that departs from prototypical IRF sequences, revealing the participants' collaborative methods of managing classroom contingencies, organizing student participation, and accomplishing the curricular focus of the lesson. (C) 2016 Elsevier B.V. All rights reserved.