The Agulhas Plateau, Maud Rise, and Northeast Georgia Rise are large oceanic plateaus previously interpreted as fragments of a single large igneous province formed at the Bouvet triple junction, and subsequently separated by rifting. However, limited age and geochemical constraints for these plateaus in the Southern Ocean have hindered a robust evaluation of this model. Here we present new 40Ar/39Ar ages from igneous rocks cored during IODP Expedition 392 on the Agulhas Plateau, together with new and compiled Sr-Nd-Pb-Hf isotope geochemistry from Agulhas Plateau, Maud Rise, Northeast Georgia Rise and the Mozambique Ridge to investigate possible cogenetic origins. Our ages indicate that the youngest magmatism on the Agulhas Plateau took place between 87 and 80 Ma. Radiogenic isotope compositions show that Agulhas lavas form a distinct compositional field characterized by relatively depleted Sr, Nd, and Hf isotopic signatures, and Pb isotope ratios that plot near the Northern Hemisphere Reference Line. In contrast, Maud Rise lavas display more enriched and DUPAL-like isotopic signatures that closely resemble those of the Mozambique Ridge, while Northeast Georgia Rise lavas have intermediate isotopic compositions. Integration of geochronological, geochemical, and seafloor magnetic constraints suggests that the Agulhas Plateau and Northeast Georgia Rise likely formed together around 90 Ma from a ridge-centered Bouvet hotspot, whereas Maud Rise more likely formed earlier together with the Mozambique Ridge. These results demonstrate that Southern Ocean oceanic plateaus formed during at least two episodes of plume-influenced magmatism associated with evolving plate boundary geometries.