Oregon Revised Statutes State Legislative Department and Laws § 171.630

(1) In case of a vacancy among the membership of an interim committee, the authority who appointed a member to the position vacant may appoint a member to fill the vacancy.

(2) For the purposes of this section, a member of an interim committee appointed in the capacity of the member as a member of the Legislative Assembly ceases to be a member of the interim committee:

(3) A presiding officer of either house of the Legislative Assembly who is a member of an interim committee may, except when serving as Governor, from time to time designate an alternate from among the members of the house of the presiding officer to exercise the powers of the presiding officer as a member of the committee.