We have analyzed wideband magnetotelluric data from three east-west transects across the Central Oregon High Cascades. The data were modelled using preliminary one-dimensional inversions of rotationally invariant parameters followed by conventional two-dimensional analysis. The resulting electrical profiles show offsets at the boundaries of the High Cascades that are consistent with downfaulting beneath the High Cascades Graben. Conductive and resistive layers in the upper crust are interpreted in terms of the known and inferred volcanotectonic history of the range. A pervasive conductor is present in the lower crust. It deepens eastward across the Western Cascades, High Cascades, and adjoining Deschutes Plateau and may indicate concomitant eastward crustal thickening. Regional heat flow and gravity studies have been interpreted as evidence of a transition from thinner crust on the west to thicker crust on the east. This transition may mark a ''suture'' between pre-Tertiary continental crust and an accreted oceanic terrane that underlies western Oregon, or it may indicate the westward limit of the anomalous lithosphere that is though to underlie the Basin and Range province. ¿ American Geophysical Union 1989