Oregon Revised Statutes Public Officers and Employees § 242.762

(1) Promotional examinations shall be given to those who desire to offer themselves for such examination and are in the qualified classifications or grades as determined by the commission. The regulations adopted for examination of applicants for promotion shall, as nearly as may be, follow the regulations governing the examination of applicants for original appointment.

(2) When there are four or more positions in a promotive grade or classification, promotional examinations for each such grade or classification in the civil service shall be given at least every 30 months and at such other times when there are no candidates eligible for promotion on the eligible register.

(3) When there are less than four positions in a promotive grade or classification, promotional examinations for each such grade or classification in the civil service shall be given at such times as it is necessary to establish an eligible register to carry out the provisions of ORS 242.702 to 242.824 as it applies to such grade or classification.