Owing to analyses of large spoken corpora the linguistic knowledge of conversation has grown in recent years exponentially. Up until now little of this knowledge has trickled down to the EFL classroom. One of the reasons, this paper argues, is the failure in the relevant literature to spell out clearly how teaching conversational grammar affects the role of what is the major variety in the EFL classroom, Standard English (SE). My aim in this paper is threefold. First, I briefly discuss some neglected conversational features in relation to SE, concluding that the contrast between the grammars of conversation and SE is so stark that the notion of SE is problematic in talking of the spoken language. Second, I consider what this contrast implies for EFL teaching, arguing that for authentic conversation to be taught effectively it is necessary to reduce the role of SE to "a core variety" that has its place in teaching writing while conversational grammar might serve as the underlying model in teaching speech. I argue that such a redefinition of SE would best be implemented in a "register approach" which shifts the emphasis from a monolithic view of language to a register-sensitive view thus acknowledging the fundamental functional diversity of language use. Third, I discuss some important issues arising from this approach and, finally, outline what may be gained by it.