Oregon is a special neighbor state and we visit frequently. It has it all. My votes would be:
anywhere along the coast especially from Florence to Depoe Bay and the 3 Capes Loop. Oregon coast S P are stunning but we favor Beverly Beach.
John Day Fossil Beds National Monument (all 3 units)
Succor Creek State park/Leslie Gulch
Wallawa Mts area in the northeast
Along I 84 and the Columbia River especially when the west side noticeably becomes the east (forests to dry scrub)
Crater Lake and Diamond Lake (Thielsen View campground has a view of Mt. Thielsen, a mountain similar to the Matterhorn with a lightning rod top)
Silver Falls State Park
Smith Rock State Park
I could go on but these are the favorites that come to mind.