The idea of grammar as a "liberating force" comes from a paper by Henry Widdowson (1990) in which grammar is depicted as a resource which liberates the language user from an over-dependency on lexis and context for the expression of meaning. In this paper, I consider the implications for second language teaching of the notion of grammar as a liberating force, and identify three key design features which, I propose, need to be present in any grammar production task in which this notion is given prominence. These are: learner choice over which grammatical structures to use; a process of "grammaticization" where the learners apply grammar to lexis; and opportunities to make comparisons and notice gaps in their use of grammar. I then discuss, with practical examples, types of grammar task which exhibit these features. These tasks all derive from traditional ELT practice, but have been revitalized to support an approach to teaching grammar which emphasizes its liberating potential.