The current study investigated a set of abilities collectively referred to as executive function (EF). Substantial improvement in EF ability occurs between 3 and 6 years of age (e.g., Carlson [2005] Developmental Neuropsychology, 28(2):595–616). This improvement is thought to reflect changes in brain development, especially in areas of prefrontal cortex and frontal cortex, which occur during this time period (e.g., Luu & Posner [2003] Brain 126:2119–2120). Little work has examined preschoolers' cortical activity during EF tasks, despite the frequent use of performance on such tasks as indirect measures of (pre)frontal functioning. The current study measured continuous EEG activity in 104 preschool aged children as they completed a battery of EF tasks. Changes from baseline to task performance in EEG activity (power, coherence) were used as predictors of EF ability. Results indicated that changes from baseline to task engagement in EEG coherence, but not EEG power, were significantly related to performance on the EF battery in our sample. © 2011 Wiley Periodicals, Inc. Dev Psychobiol 53:771–784, 2011.