Grammar instruction is an unresolved issue in the Hispanic area, having long been approached from within the disjunction between rhetoric (teaching how to use language, especially writing) and grammar (teaching the grammar content). Over time grammar instruction has generated an intense debate around two positions: direct instruction on grammar content, versus instruction devoted to prompting reflection on grammar and language use. There has been an insistent and recurring tendency towards the former, a situation that still prevails. More recently, however, certain research trends in Spain, albeit a minority, have crystallized in a research trajectory on metalinguistic activity, opening up new possibilities for rethinking instruction based on grammar reflection to support writing. Within such a trajectory, innovative ways to promote grammar reflection within language use are explored, and metalinguistic activity becomes the focus of research and pedagogy. Crucially, some of the empirical studies developed within this trajectory suggest that grammar knowledge may not be a condition for reflection about language but its consequence, leading to a consideration of metalinguistic activity as a promising avenue for rethinking the debate on the role of grammar instruction.