Metacognition is a topic of increasing interest in the field of instruction and learning, but its relation to actual teaching behaviors is seldom investigated in second language (L2) classroom research. The purpose of this study was to examine whether and how language teacher metacognition and executive function are linked to high-leverage teaching practice. We recruited foreign and second language teachers (N = 937), including bilingual/ESL teachers, from public schools across the southern United States. We obtained a direct measure of teachers' executive function and an indirect measure of metacognitive capacity. Using the Tripod (7Cs) framework, we also assessed specific aspects of high-leverage teaching practice under 3 broad conceptual areas: personal support, curricular support, and academic press. We examined the mediating role of teacher metacognitive capacity between executive function and exemplary classroom practice, and tested an alternative model. Analyses returned stronger support for our hypothesized model over the alternative, indicating that teacher metacognition--teachers' adaptive capacity to monitor, interpret, evaluate, and intervene on L2 classroom events--constitutes an important mediating condition for building classroom environments that are engaging, demanding, and supportive of learners' L2 development.