Little Canyon Mtn. is just outside of John Day, and will have an old Hydraulic mine pit open for 4x4's in the new management plan, but don't think it is up and running yet. North of there is Morrow Co. OHV area with some 4x4 stuff. Over by Baker City is Virtue Flat, 5000 acres open to cross country travel with trals in there from mild to wild.
An OHV permit is required when wheeling on public land in the state, but not expensive (10.50 for 2 years), reciprocity if your state allows Oregon OHV permits.
For a map of trails at Virtue, hit BLM office in Baker City-Talk to Kevin McCoy there, he uses Virtue all the time. John Day contact BLM in Prineville. We will also be getting a small open area up by Kimberly in the near future but no open yet.
Also have dunes over on the coast, and down at Christmas Valley-About 6000 acres there open to us.
Up on Santiam Pass on Hwy 20 west of Bend/Sisters is a nasty trail called Quack Attack that you really need to be minimum 33's and a locker or winch, and happier if on 35's or better. Contact Deschutes County 4 Wheelers for that one. Opens after snow is gone. Club will do a work party/opening in July. End of June they will also do a rock crawl at an old borrow pit called Groundhog Quarry, SE of Bend.
For OHV regs/areas, contact Oregon State Parks and Recreation-ATV program. Also general maps of most areas listed in the ATV reg booklet can be found at: rideATVoregon.
The PNW4WDA, Region 6 clubs do a Father's day run on the McGrew trail in SW Oregon out of Cave Junction, About 14 miles of an old 1850's wagon road that serviced the gold camps. Registration cut off is June 1st for that. Klamath Falls 4 Runners is the contact point.
All of the above can be found by a search on the net. Welcome to our little part of paradise. Hope this helps.
I am the OHV representative on a BLM Resource Advisory Committee for the NE 1/4 of the state and a little bit of WA and ID. Anything I can do to help, let me know.