Attention and working memory are two cognitive abilities that have been the target of research to determine whether they are independent (Baddeley, 2003) or related constructs (Kiyonaga & Egner, 2013). Modifying traditional attention tasks to incorporate a working memory component allows direct investigation of this question. The first aim of the present study was to provide further evidence of the relatedness of attention and working memory by measuring behavioral and electrophysiological markers in a modified Stroop task (internal task originally developed by Kiyonaga & Egner, 2014). A second, related goal was to determine the extent to which the Dual Mechanisms of Control (DMC) theory (Braver, 2012) adequately explains patterns found in response to this modified Stroop task. Cognitive control is the process through which an individual maintains goal-directed behavior in the presence of ambiguous or conflicting information (i.e., staying on task; Abrahamse, Braem, Notebaert, & Verguts, 2016). The DMC theory states that there are two types of cognitive control—proactive and reactive—which have been dissociated in traditional distractor-interference attention tasks (Braver, 2012). Finally, the current study aimed to determine the extent to which young and older adults utilize similar control mechanisms in response to the modified Stroop task. The DMC proposes that aging results in diminished proactive but relatively preserved reactive control (Braver, Paxton, Locke, & Barch, 2009). The task used a list-wide proportion congruency manipulation in order to elicit conditions of proactive control (Gonthier, Braver, & Bugg, 2016). Results indicated a reduced Stroop interference effect in the mostly incongruent block compared to the mostly congruent block, evidence of Stroop interference disrupting response times to later memory retrieval, and confirmation of Flanker-like N2 effects in the ERP results of the internal task (Faust et al., 2017; 2018). Limited behavioral evidence for proactive control was found, as neither transfer effects nor congruency costs were found. Age-related results include a reduced Stroop interference effect in mean response times for older adults compared to young adults, a greater disruption in word retrieval time for older adults than for young adults, and differential ERP patterns found for young and older adults.