Quick answer: no — Oregon does not let a surviving spouse add a deceased spouse's unused exemption to their own. Run your own numbers in the Oregon estate tax calculator.
One exemption per spouse, no exceptions
Each spouse has their own $1,000,000 Oregon exemption. If the first spouse to die doesn't use all of it, the unused portion simply disappears — there's no mechanism in ORS Chapter 118 to carry it forward to the survivor, the way federal portability works.
The Oregon special marital property election
It can even reach multi-beneficiary trusts
If a trust would otherwise qualify except that it allows distributions to other beneficiaries too, the executor can carve out a separate share or trust as Oregon special marital property — but only if every other permissible distributee, and the surviving spouse, sign a written consent agreeing to give up any current interest in that carved-out share during the spouse's lifetime.
A separate election, independent of the federal return
If the federal taxable estate is determined using certain elections under the Internal Revenue Code, or no federal return is required at all, the executor may make a separate Oregon-only election for state estate tax purposes under that same provision — the Oregon and federal marital deduction decisions don't have to match.
A local probate attorney can review your estate — many offer a free consultation.
Every election under ORS 118.013 and 118.016 is irrevocable once the paperwork is filed with the estate tax return — have a licensed Oregon attorney confirm the trust language qualifies before committing to it.