Good Sam campsite/RV park book lists most COE's in Oregon.
The ones we've visited have always been clean and spacious. Many are managed by county parks. We like them because they are almost always situated on water as (ACOE has many dams in Oregon).
A couple we have enjoyed are:
Pine Meadows Campground (Cottage Grove Lake)
Sunnyside Campground (Timothy Lake and Santiam River)
Tyee Campground (on the coast, just south of Florence)
Some of the facilities are more primitive, with vault toilets and potable water, but well maintained. Very few have hookups. They are often managed in conjunction with other governmental entities (USFS, County, Dept of Fish and Wildlife). Here in Oregon, they are mostly seasonal
We find it very difficult to find camping spots from October - March. I suppose it's the weather and many of the campers go South for the Winter. And, since the campgrounds are usually hosted, there are budget restrictions.
We are fortunate, in our area, to have several County and State Parks that are open year-round.