The high elevation and considerable length of the Transantarctic Mountains have led to speculation about their origin. To date, no model has been able to adequately reconcile the juxtaposition of the high, curvilinear Transantarctic Mountains with the adjacent West Antarctic Rift System, a broad region of thin extended continental crust exhibiting wide rift characteristics. We present a first-order investigation into the idea that the West Antarctic Rift System–Transantarctic Mountains region was a high-elevation plateau with thicker than normal crust before the onset of continental extension. With major Cretaceous extension, the rift underwent a topographic reversal, and a plateau edge with thickened crust, representing the ancestral Transantarctic Mountains, remained. In the Cenozoic, minor extension and major denudation reduce the crustal root while simultaneously uplifting peak heights in the mountains. The Cretaceous stage of this concept is investigated using two-dimensional numerical models to determine under what conditions plateau collapse is plausible. Model results indicate that elevation of a remnant plateau edge decreases with increasing initial Moho temperature. Very cold initial Moho temperatures, <675 °C, under the plateau leave a thick plateau edge but do not exhibit wide rifting. A cold to moderate initial thermal structure, Moho temperatures of 675–850 °C, is needed to retain the plateau edge and still exhibit wide rifting in the middle of the plateau. We conclude that this plateau collapse concept is possible using these numerical experiments, and that application of this idea to the West Antarctic Rift System–Transantarctic Mountains system is also supported by geological and geophysical evidence.