Oregon Constitution Art. II § 2

(a) Is 18 years of age or older;

(b) Has resided in this state during the six months immediately preceding the election, except that provision may be made by law to permit a person who has resided in this state less than 30 days immediately preceding the election, but who is otherwise qualified under this subsection, to vote in the election for candidates for nomination or election for President or Vice President of the United States or elector of President and Vice President of the United States; and

(c) Is registered not less than 20 calendar days immediately preceding any election in the manner provided by law.