Not really organized, but;
Crater Lake loop, before they open the road to cars.
Steens Mountain Loop road, before they open the road to cars.
McKenzie Highway, before they open the gates....for cars.
I've ridden the Crater Lake loop, have not done the other two. With the abundant snowpack it may be August.
If you are in Bend, come out for the Web Cyclery spring ride, April 13th.
http://webcyclery.com/home.php