Oregon Revised Statutes Revenue and Taxation § 316.042

In the case of a joint return of spouses in a marriage, pursuant to ORS 316.122 or pursuant to ORS 316.367, the tax imposed by ORS 316.037 shall be twice the tax which would be imposed if the taxable income were cut in half. For purposes of this section, a return of a head of household or a surviving spouse, as defined in subsections (a) and (b) of section 2 of the Internal Revenue Code,  1 shall be treated as a joint return of spouses in a marriage.