Oregon Revised Statutes Procedure in Criminal Matters Generally § 136.230

(a) The defendant may challenge two jurors and the state may challenge two, and so alternating, the defendant exercising two challenges and the state two until the peremptory challenges are exhausted.

(b) After each challenge the panel shall be filled and the additional juror passed for cause before another peremptory challenge is exercised. Neither party shall be required to exercise a peremptory challenge unless the full number of jurors is in the jury box at the time.

(c) The refusal to challenge by either party in order of alternation does not prevent the adverse party from exercising that adverse party's full number of challenges, and such refusal on the part of a party to exercise a challenge in proper turn concludes that party as to the jurors once accepted by that party. If that party's right of peremptory challenge is not exhausted, that party's further challenges shall be confined, in that party's proper turn, to such additional jurors as may be called.