Most experimental preparations demonstrate a role for dorsolateral striatum (DLS) in stimulus-response, but not outcome-based, learning. Here, we assessed DLS involvement in a touchscreen-based reversal task requiring mice to update choice following a change in stimulus-reward contingencies. In vivo single-unit recordings in the DLS showed reversal produced a population-level shift from excited to inhibited neuronal activity prior to choices being made. The larger the shift, the faster mice reversed. Furthermore, optogenetic photosilencing DLS neurons during choice increased early reversal errors. These findings suggest dynamic DLS engagement may facilitate reversal, possibly by signaling a change in contingencies to other striatal and cortical regions.