Unless it's hunting season, there is nice dispersion camping at the Summer Lake Wildlife refuge. Just turn right off 31 at the BLM office (before the rest stop) and you'll figure it out.
If it's busy (only in hunting season) at the Wildlife refuge, there's tons of spots in the NF along 31 about 16 miles SE of hwy 97.
Once on 97 (near LaPine), there isn't a lot of great (dispersion) places unless you go a little way's from the road. Indeed, not much for quite a longgggg way....unless you get off the road. Might wind up in a dreaded CG.
There is a super nice roadside wayside north of Moro (DeMoss County Park) where you could overnight.
Up near Ruffis, some folks stay on US Army Corps of Engineering land along the Columbia river. Have never checked it out myself though.
