The Cretaceous period was marked by the most voluminous episodes of oceanic plateau volcanism in the Phanerozoic Eon. Primarily affecting the Pacific, mantle plumes generated oceanic plateaus during three main phases (ca. 145–140 Ma, ca. 122–115 Ma, and ca. 100–90 Ma). Central America is one of the very few circum-Pacific margins where remnants of these Cretaceous plateaus were accreted. The study of their onland exposures provides a highly valuable insight into the complexity and diversity of oceanic plateau histories, from their eruption to their accretion. Exposed in northern Costa Rica, the plateau remnants of the Nicoya Peninsula originated from a Jurassic oceanic crust over-thickened by Early and Late Cretaceous hotspots. These sheared-off pieces of the Farallon Plate testify to the early tectonic interaction of the Caribbean Large Igneous Province (CLIP, ca. 94–89 Ma) with North America, initiated <5 m.y. after the onset of CLIP eruption. By combining our results with previously published data, we propose an updated tectono-stratigraphic framework that divides the Nicoya Peninsula into two oceanic plateau terranes. (1) The accretion timing of the Aptian to Turonian Manzanillo Terrane is constrained by the Coniacian (ca. 89–86 Ma) base of the overlapping Loma Chumico Formation. The proximal tuffaceous forearc deposits of the Loma Chumico Formation are the oldest evidence of a volcanic arc in Costa Rica—called here the Berrugate Arc—as revealed by new biostratigraphic and geochemical data. (2) The Nicoya Complex s. str. is a composite plateau remnant containing rocks of Bajocian to earliest Campanian age. Its accretion occurred during the middle Campanian (ca. 79–76 Ma) and shut down the Berrugate Arc. In contrast to the collision of CLIP with North America, onset of the collision of CLIP with South America began much later, during the latest Campanian (ca. 75–73 Ma).