Low-frequency activity within the oculomotor system helps bridge sensation and action. Given ocular stability, low-frequency activity sustained by some neurons within the intermediate and deep superior colliculus (dSC) is assumed to be separated from motor output. However the dSC is an orienting structure and the influence of low-frequency dSC activity at other effectors remains untested. We studied this by simultaneously recording activity from saccade-related dSC neurons and electromyographic activity from neck muscles that turn the head. Monkeys performed a gap-saccade paradigm with varying levels of reward expectancy. Despite head-restraint and even for relatively small target eccentricies (10), increasing reward expectancy for a given target increased the level of low-frequency activity on dSC neurons encoding saccades to the rewarded target, and increased the recruitment of a neck muscle synergy that would turn the head toward the target. The magnitude of neck muscle recruitment correlated positively on a trial-by-trial basis with the level of low-frequency dSC activity, and such correlations were optimized when neck muscle activity was shifted ~20 ms later to account for delays in the tecto-reticulo-spinal pathway. Further, dSC activity discriminated about the side of target presentation ~11 ms earlier than neck EMG activity. Considered alongside neck EMG responses evoked causally by SC stimulation, our results are consistent with low-frequency dSC activity recruiting a head-turning synergy. Our results support a brainstem circuit wherein the magnitude of neck muscle recruitment reflects the difference in comparative low-frequency activation across both dSC, perhaps because of mutually inhibitory interactions within downstream head premotor circuits.