Recent work suggests brain signal variability tracks maturational changes in information processing capacity. Evidence also suggests variability changes with task demands. Here, we investigate whether there is an interaction between age and task related changes in brain signal variability measured with electroencephalography (EEG). We looked at brain signal variability changes during different epochs within trial (i.e., before to after stimulus onset, and after response) and with task difficulty, in children (age 8-14) and adults (age 18-33). In the epochs within trial analysis, we found similar changes pre- to post-stimulus onset in both age groups, but a later return to baseline in children then adults. In the task difficulty analysis, variability changed with difficulty conditions only in children. Our data suggest that age-related differences in variability changes with task reflect differences in the cognitive processing performed by children and adults during task performance.