The quiet eye phenomenon describes the performance advantage conferred by a steady ocular fixation on the critical target of an action (e.g., the ball in golf putting) immediately prior to and during movement execution. Remarkably, the mechanisms underlying the quiet eye-performance association are still the subject of debate. This study adopts a novel multi-measure psychophysiological approach to shed light on the mechanisms behind the quiet eye phenomenon. We tested key predictions of two competing mechanisms: that longer quiet eye is associated with enhanced visual processing (visual hypothesis) or with greater postural-kinematic stability (postural-kinematic hypothesis). Thirty-two recreational golfers putted 20 balls to a 2-m distant target on a flat surface. We examined quiet eye durations using electrooculography, visual processing using electroencephalography, and swing duration using kinematic sensors. Occipital alpha power, an inverse neural marker of visual processing, increased prior to and during swing execution, suggesting decreased visual processing compared to a pre-putt baseline. Importantly, quiet eye duration was strongly and positively correlated with swing duration. Our findings refute the claim for enhanced visual processing in the final moments of closed-loop aiming tasks and support the postural-kinematic account that the duration of the quiet eye is associated with a slow movement execution.