In addition to the small estate probate process already mentioned, you may be able to just use an Inheritance Affidavit.
See the form here: http://www.odot.state.or.us/forms/dmv/516fill.pdf
See more information in general from the DMV here: http://www.oregon.gov/ODOT/DMV/vehicle/inherit.shtml
The form has to be signed by all heirs, as determined by Oregon statute. The general order of heirship is as follows:
1. Surviving spouse if there are no children, or if all children are from that relationship
2. Surviving spouse and children if there are children from previous relationship(s)
3. Issue (children, and grandchild of a predeceased child)
6. Grandparent(s) (or aunts/uncles if grandparents are deceased)
In your case, you are in spot #5 on the list. You can complete the Inheritance Affidavit with the DMV if there are no surviving family members from any of the spots #1-4.