Although grammatical inquiry competence has been considered as an imperative objective in grammar education, its construct has not been clearly specified. Therefore, to fill this gap, the present study aims to investigate the assessment of grammatical inquiry competence as follows. First, we critically reviewed a current state of assessing grammatical inquiry competence by examining the grammar assessment framework of National Assessment of Educational Achievement and the grammar achievement standard of Korean Language Arts’ Curriculum. Second, we specified the notion of grammatical inquiry competence and proposed the framework of grammatical inquiry competence, which is likely to meet the objectives of Korean Language Arts’ Curriculum. Third, based on our argument, we suggested the framework of the measurement of grammatical inquiry competence. This approach will be a meaningful step not only for developing tools for measuring grammatical inquiry competence but also for establishing a pedagogical foundation of grammar inquiry learning. Also, ultimately, this study will shed light on the importance of grammar inquiry learning.