While literature suggests the significance of peer interaction for language learners, little is known about how the interaction specifically works to benefit them. Additionally, while putting students in groups has become a widespread practice in language classrooms, most teachers appear not to have a clear idea of how to structure classroom interaction and cooperation so that learning goes in the direction of helping learners to attain communicative competence. To address the gap in the literature and lessen the theory-practice contrast, this qualitative case study was conducted by looking at how cooperative learning (CL) processed in EFL classrooms, with specific attention given to how individual accountability--CL's key principle--manifested and played its important roles during speaking lessons. One of the findings shows that CL's peer interaction in individual accountability activities provides EFL learners with opportunities for giving and receiving vocabulary help, which later helps them to perform better in presenting their understanding of the materials. By implementing CL with fidelity, teachers help EFL learners to achieve their language learning objectives. As for teacher educators, they need to engage teachers in the activities of zooming in on how CL's structured interaction and cooperation help enhance EFL learning.