The language control processes used by multilinguals to monitor and control their language use are commonly investigated in the lab using picture naming paradigms in which participants are instructed when to switch between languages. However, language switching in daily life often occurs freely when interlocutors share multiple languages, a process which is rarely studied using neuroimaging. This study investigates the electrophysiological manifestation of switching effects in voluntary compared to cued language switching. Cued language-switching tasks usually show slower responses on trials in which participants switch to a different language (switch trials) compared to no-switch trials (repeat trials) (i.e. switching cost; e.g. Meuter & Allport, 1999). Previous behavioural studies found this switching cost could be the same (de Bruin et al., 2018) or smaller (Jevtović et al., 2020) in voluntary compared to cued switching, or even absent (Blanco-Elorrieta & Pylkkänen, 2017). It could be that less top-down control of the non-target language is required when speakers are free to choose their language and can simply use whichever words come most easily (e.g. Green, 1998). In the present study, adult Dutch-English late bilinguals perform two picture-naming tasks in which they are required to switch between Dutch and English, while EEG is recorded. In one task, they are requested to use both languages, but can decide the language for each trial voluntarily, while in the other, language is cued by the background colour of the image. For control purposes, the voluntary task alternates between two backgrounds as well. This results in a 2*2 design with the variables task (voluntary/cued) and trial (switch/repeat). The analyses in this study focus on the N2 ERP component and mid-frontal theta oscillations, two common electrophysiological markers of cognitive control in task switching. Earlier cued language switching studies have found an N2 switch effect (e.g. Jackson et al., 2001) and a mid-frontal theta switch effect (unpublished analysis of data from Zheng et al., 2020). The properties or size of these top-down control markers could differ between repeat and switch trials, as well as between voluntary and cued switching. Previous research in the speech production and task-switching literature has found N2 effects in relation to various types of top-down control, and other non-linguistic studies show higher mid-frontal theta power for trials that require more cognitive control (e.g. Eisma et al., 2021). Therefore, it is plausible that the electrophysiological switching cost (the difference between the N2 amplitude or mid-frontal theta power in switch versus repeat trials) is bigger in the cued task than the voluntary task. This study was pre-registered. Currently, half of the 24 intended datasets have been collected. The study’s results and conclusions will be presented, providing new insights into the neural processes of language control behind voluntary switching in multilinguals. Our results will also aid neuroimaging research on multilingual processing to better reflect the variety in real-life multilingual experiences.