The evidence for the treatment in Oscan of *- u- after a coronal is examined. In the areas which use the Oscan alphabet (Campania and Samnium), this has become [i̯u]; in the areas which use the Greek alphabet (Lucania and Bruttium) it has become [y]. Contrary to previous assumptions, there is evidence for a change to [y] in the Latin-alphabet Tabula Bantina from Lucania, since the <i> in the forms petiropert ‘four times’ and manim ‘hand’ is most easily explained as coming directly from *- u-. Evidence from both relative and absolute chronology shows that this difference must be a dialectal rather than a chronological split between Campania-Samnium and Lucania-Bruttium, since the different reflexes of *- u- are already in place by the time of our earliest evidence, and are maintained throughout the history of Oscan.