In the form preparation task, participants verbally produce words in small sets, which either overlap on an early phonological fragment or contrast on that fragment. A canonical account of word-form encoding assumes a sequential phonological encoding phase necessarily preceding subsequent retrieval of a discrete phonetic motor plan. This account assumes that acoustic onset and speech onset are equivalent, and that speech onset never precedes complete processing of the stimulus. In two form preparation experiments, we examined the influence of anticipatory processes on preacoustic lip articulation. We used motion-tracked digital video to measure continuous changes in vertical lip aperture. In sets with initial segment overlap, participants configured their lips to anticipate upcoming aerodynamic demands, before stimulus presentation. Anticipatory posturing arose even when initial segment was only 75% certain. These findings appear inconsistent with extant speech models that assume ballistic execution of a fully encoded, certainly known response. (PsycINFO Database Record (c) 2019 APA, all rights reserved).