Brain dynamics research has highlighted the contributions of the ongoing EEG to ERP and behavioural responses. This study examined the effects of state-related EEG changes, from rest to the task and within the task, on stimulus-response efforts in a visual Continuous Performance Test (CPT). EEG was recorded from fifty-six adults at rest with eyes-closed (EC) then eyes-open (EO), and during the CPT. Principal Components Analyses decomposed the EEG obtained from EC, EO and the task-based periods immediately pre-cue (PC) and pre-imperative (PI), and the ERPs to the cued Go/NoGo imperatives. EC amplitudes were correlated with Go/NoGo ERP amplitudes and behavioural outcomes. EEG amplitude changes from EO to PC, and from PC to PI, were assessed as predictors of these response measures. Longer mean reaction time (RT) was associated with greater RT variability (RTV) and reduced Go P2. The two EC alpha components correlated positively with RTV, and NoGo P1 and P2 positivity. Delta/theta amplitude reductions from PC to PI predicted Go N1-1 and NoGo N2b enhancements. Alpha-1 decreases from PC to PI predicted larger P2 and poorer NoGo accuracy rates, while alpha-3 decrements positively predicted NoGo P1. These findings highlight the ongoing alpha arousal effects on stimulus-response efforts, and the low frequency shifts in the cue to imperative interval associated with stimulus anticipation and response preparation. These relationships offer novel insights into the effects of pretask EEG activity, and within-task EEG changes, on attention and cognitive control processes.