Oregon Revised Statutes Probate Law § 112.580

(1) Except as provided in ORS 112.586, if property is held by two co-owners with right of survivorship and both co-owners are deceased, one-half of the property passes as if one co-owner had survived the second co-owner by 120 hours or more, and one-half of the property passes as if the second co-owner had survived the first co-owner by 120 hours or more, unless it is established by clear and convincing evidence that one of two co-owners survived the other co-owner by at least 120 hours.

(2) Except as provided in ORS 112.586, if property is held by more than two co-owners and it is not established by clear and convincing evidence that at least one of the owners survived the others by at least 120 hours, the property passes in the proportion that one bears to the whole number of co-owners.