The Dual Mechanisms of Control theory proposes that individuals flexibly alternate between two modes of control β reactive and proactive β based on current task demands (Braver, 2012). In imaging studies, reactive control is correlated with transient activity in the lateral prefrontal cortex (PFC) and the anterior cingulate cortex, while proactive control is associated with sustained activity in the lateral PFC. Research using event-related potentials (ERPs) has identified the frontal slow wave (FSW) as a neural marker of proactive control (Bailey, West, & Anderson, 2010; West & Bailey, 2012; West et al., 2012). The current study aimed to replicate and extend previous work by examining slow wave activity in a counting Stroop task. The counting Stroop, like the traditional color-word Stroop (Stroop, 1935), requires participants to respond to stimuli with features that are congruent or incongruent to their task goals, making it ideal for examining the use of cognitive control. In the current study, the proportion of congruent and incongruent trials was manipulated in order to encourage participants to rely on reactive or proactive control. Additionally, the response-to -stimulus interval (RSI) was varied to examine the effect of task timing on the implementation of control. The data revealed that both the proportion of congruent trials and the RSI influence which type of control is utilized. The presence of slow wave activity during mostly incongruent blocks of trials and longer RSIs further supports its association with the implementation of proactive control