Assessing cognitive load may be useful in a variety of applications, especially in identifying the onset of high cognitive load. However, current methods do not exist that can pinpoint such an event. We recorded EEG from participants while they completed auditory oddball paradigm and Stroop tasks. To determine the time at which a change in cognitive load could be detected, we applied auditory tones at four time points before and after the onset of an incongruent Stroop trial: (1) 100 ms prior to the Stroop onset, (2) 100 ms post Stroop onset, (3) 300 ms post Stroop onset, and (4) 450 ms post Stroop onset. Event-related potential results suggest that cognitive load was highest at time points after 100 ms post Stroop onset. This work provides a method for identifying an increase in cognitive load, which could be an important diagnostic tool for device development and tuning.