Spiessbraten is Idar-Oberstein's local food ritual: meat cooked over a wood fire, usually served plainly, with the smoke doing most of the talking. It is not refined cooking, and it should not be.
Several restaurants in and around Oberstein serve it, including old-town places used to visitors coming down from the Felsenkirche. Order it when you are hungry; this is a meal for after a climb, not before one.