Per the Oregon Department of Revenue Frequently asked questions webpage:
If you want your Oregon refund apportioned between spouses, you need to request it in writing. When your return is processed, we'll notify you of our intent to apply the joint refund to any debts owed to the state of Oregon. When you receive our notice, send us a request to divide the refund. You must respond within 30 days of the date on our notice. You can use federal form 8379, Injured Spouse Allocation. We must have a copy of your federal return to process the apportionment.
Address your refund request to:
Oregon Department of Revenue
955 Center St NE
Salem OR 97301-2555
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the webpage or document at the time it is accessed.