The present study investigated the feasibility of acquiring high-density event-related brain potential (ERP) recordings during treadmill walking in human subjects. The work builds upon recent studies testing the applicability of real-world tasks while obtaining electroencephalographic (EEG) recordings. Participants performed a response inhibition GO/NOGO task - designed to evoke a P3 component for correct response inhibitions and an error-related negativity (ERN) for incorrect commission errors - while speed of walking was experimentally manipulated. Robust P3 and ERN components were obtained under all experimental conditions - while participants were sitting, walking at moderate speed (2.4 km/hour), or walking rapidly (5 km/hour). Signal-to-noise ratios were remarkably similar across conditions, pointing to the feasibility of high-fidelity ERP recordings under relatively vigorous activity regimens. There is considerable research and clinical motivation to obtain high quality neurophysiological measures under more naturalistic environmental settings such as these. Strong links between cognitive load and gait abnormalities are seen in a number of clinical populations and these MoBI technologies provide highly promising methods for gaining insights into the underlying pathophysiology.