<p>Task cues are often used to study task preparation. Participants are thought to activate cued task sets in advance to facilitate later task performance. Earlier studies showed that task performance was improved, if the relation of cue and decision categories of the task was more transparent, suggesting a facilitated task preparation process with more transparent cues. However, no previous study directly tested how processing differs between cues with varying transparency in the cue interval itself. To this end, we analyzed cue-locked event-related potentials (ERPs) and oscillatory activity of the electroencephalogram (EEG) for four different cue types with varying cue transparency. An increased cue-locked positivity ERP component indicated the largest preparation demands for arbitrary symbol string cues, which lacked any apparent relation with the cued task. Moreover, visual demands reflected by an early positive deflection and task set reconfiguration demands reflected by theta oscillations were increased for both word cues (decision categories used as cues) and symbol string cues, indicating that cues with a higher visual complexity pose additional demands on visual and cognitive cue processing. In contrast, these electrophysiological correlates of preparation demands were lowest for letter cues. Hence, if one wants to facilitate cue-induced task set activation, simple letter cues appear beneficial. In conclusion, task cue transparency influenced electrophysiological correlates related to the preparatory demands required for task set retrieval and should therefore be taken into account when studying task preparation.</p>