In the neurobiology of syntax, a methodological challenge is to vary syntax while holding semantics constant. Changes in syntactic structure usually correlate with changes in meaning. We approached this challenge from a new angle. We deployed word lists—typically the unstructured control in studies of syntax—as both test and control stimuli. Three-noun lists ( lamps, dolls, guitars ) were embedded in sentences ( The eccentric man hoarded lamps, dolls, guitars …) and in longer lists ( forks, pen, toilet, rodeo, lamps, dolls, guitars …). This allowed us to minimize contributions from lexical semantics and local phrasal combinatorics: the same words occurred in both conditions and in neither case did the list items locally compose into phrases (e.g. ‘ lamps ’ and ‘ dolls ’ do not form a phrase). Crucially, the list partakes in a syntactic tree in one case but not the other. Lists-in-sentences increased source-localized MEG activity at ∼250-300ms from each of the list item onsets in the left inferior frontal c...