While admittedly a bit contrived, this route links up the majority of the best gravel in the area, combining lots-o-climbing, stellar views and some really cool, remote hardpack on Hastings Ridge.
I’d skip Hastings Road when there’s any chance of mud – it’s likely impassable by skinny-tired bikes when wet.   Use the map referenced below for alternates – everything in the area is primo riding.
For those who get crushed by the route there’s the defeated King Harold finish which takes a flatter, paved route back to the Dalles.   This option skips about 600 ft. of climbing and a bunch more gravel.