Based on a synthesis of classroom SLA research that has helped to shape evolving perspectives of content-based instruction since the introduction of immersion programs in Montreal more than 40 years ago, this book presents an updated perspective on integrating language and content in ways that engage second language learners with language across the curriculum. A range of instructional practices observed in immersion and content-based classrooms is highlighted to set the stage for justifying a counterbalanced approach that integrates both content-based and form-focused instructional options as complementary ways of intervening to develop a learner’s interlanguage system. A counterbalanced approach is outlined as an array of opportunities for learners to process language through content by means of comprehension, awareness, and production mechanisms, and to negotiate language through content by means of interactional strategies involving teacher scaffolding and feedback.