Being error prone, the context of visual behavior must be monitored to achieve goals. Previous work in monkeys performing a saccade countermanding task has demonstrated modulation of signals in the supplementary eye field in response to visual information and conflict between mutually incompatible visuo-motor plans. However, the laminar distribution of these signals is unknown. We present neurophysiological data from two monkeys collected using a linear electrode array during visual saccade countermanding task. Monkeys were rewarded for making a saccade to a visual target; however, in infrequent, random trials a stop signal appeared instructing the subject to cancel this pre-planned saccade. These stop signal trials engendered conflict between the competing GO and STOP processes. From 16 perpendicular penetrations, we isolated 293 neurons across all SEF layers. Significant modulation to a visual target was noted in 80 neurons, with a mean latency of 71 ± 20 ms. Spiking activity was concentrated in layers 2 to 5 and absent in layer 6. Visual neurons with wide spike widths were distributed throughout the cortex, but those with narrow spikes were primarily concentrated in layer 3. In trials associated with lower reward amounts neurons demonstrated higher visual responses, most pronounced in the latter period of the visual response. Significant modulation when monkeys had to withhold a pre-planned movement to a target was noted in 18 of these visual neurons, and in 50 neurons in total. These cells were primarily concentrated in layers 2, 3 and 5. Conflict-responsive neurons with narrow spikes (n=21) were located significantly more superficially than those with wide spikes (n = 29), U = 403.50, p=0.009. These findings further delineate the mechanisms of medial frontal cortex in performance monitoring. The contribution of laminar specific signals constrains circuit-level models of executive control and guide further inverse modelling solutions of visual performance event-related potentials.