This systematic conceptual mapping review investigated definitions of instructional quality in secondary language arts (LA) research. Although LA inherently integrates multiple competencies, such as reading, writing, and oracy, educational research frequently isolates topics, thus limiting comprehensive definitions and overarching instructional frameworks. By analyzing 39 studies from 2000–23, we identified nine core quality themes representing varied definitions of instructional quality, notably including competence support, intellectual challenge, fostering a community of learners, student engagement, and instructional coherence. Our findings identified a critical epistemological tension between linear conceptions of quality, focusing on isolated instructional practices, and systems-oriented approaches, emphasizing dynamic interactions within instructional contexts. Results emphasized the need for integrated frameworks to better capture the complexity and multidimensionality of quality in secondary LA education. This review contributes to ongoing discussions regarding instructional quality, offering a nuanced synthesis to inform teacher education, professional development, and future research frameworks in LA secondary education.