This article takes the view that grammar is driven by user choices and is therefore complex and dynamic. This has implications for the teaching of grammar in language teacher education and how teachers' cognitions about grammar, and hence their own grammar teaching, might change. In this small, interpretative study, the participants--students on an MA programme in the United Kingdom--were taught grammar from a functional perspective, but with mainly traditional classifications and metalanguage. They were required to negotiate solutions to grammar tasks designed to provoke "cognitive conflict" (Tocalli-Beller, 2003) when the authentic language use of the texts did not conform to their prior knowledge. This was assumed to stimulate a high quality of engagement with language (EWL; Svalberg, 2009), thus facilitating the construction of new or enhanced knowledge about grammar. Analysis of the participants' learner diaries, interviews, and workshop interactions reveal that cognitive conflict is an essential factor in the emergence of new understandings of complex grammar features and of grammar as meaning in context. The study contributes to the literature on inquiry-based approaches to language learner education by the insights it provides into knowledge creation in such environments.