The neurocognitive basis of bilingualism has attracted substantial research attention, particularly regarding whether managing two language systems produces measurable advantages or costs in domain-general executive control functions including working memory, inhibitory control, and cognitive flexibility. The bilingual advantage hypothesis, prominent from approximately 2004 to 2015, has been substantially complicated by subsequent large-sample studies and meta-analyses reporting inconsistent or null effects. This study examined working memory capacity, cognitive inhibition, and language switching costs in 148 late French-English bilinguals and 72 French monolinguals at the Université libre de Bruxelles using event-related potential (ERP) neuroimaging, mixed-language Stroop task reaction times, and N-back working memory paradigms.Results revealed significant language switching costs in the bilingual group, with incongruent Stroop interference effects of 196 ms in the second language (L2) compared to 136 ms in the first language (L1). ERP analysis identified a larger N2 component amplitude in bilinguals during incongruent Stroop trials, suggesting enhanced early conflict monitoring as a bilingual cognitive adaptation. N-back accuracy was significantly lower in L2 conditions (81.3% vs. 88.4% in L1), indicating a working memory cost under dual-language processing demand. Language dominance, switching frequency, and age of L2 acquisition emerged as significant moderators, partially reconciling the inconsistent bilingual advantage literature.