There’s a magical fatbike heaven buried deep in the bowels of Oregon. This is the best fatbiking we’ve found in Oregon (so far) and highly recommend it. Camping on-sight is free, just bring your own water, guns and whiskey. Also, you’ll have to share it with a handful of ATVs and motos, but with 20-ish square miles of sand dunes to explore, solitude is easy to find.
Close by, and also recommended are Fort Rock, Crack in the Ground, camping on Green Mountain, and exploring the local cinder cones.