Part of the High Cascades segment of the larger Cascade Range, Olallie Butte is part of a stretch of shield volcanoes in Oregon with an unusually low elevation, meaning they have undergone less erosion over time than surrounding volcanic centers. Olallie Butte forms part of the Jefferson Reach, an axis of shield volcanoes, scoria cones, and lava domes in width that contains at least 175 Quaternary volcanoes. The Jefferson Reach's northern portion has an unusually low number of young volcanic centers (early Pleistocene or younger). The subsection including Olallie Butte consists mostly of Pleistocene or younger volcanoes, which are often glaciated. Of these volcanic vents, Olallie Butte and Sisi Butte are the two largest mafic (rich in magnesium and iron) shield volcanoes. Olallie Butte marks part of a region of basaltic andesite eruptions, also prominent at Three Fingered Jack, that extends north and south from Mount Jefferson.