Oregon Revised Statutes Elections § 255.185

(1) In a district that holds regular district elections, if an initiative or referendum petition contains the required number of verified signatures, the election on the district measure shall be held on the third Tuesday in May, the first Tuesday after the first Monday in November or the date of the next scheduled regular district election. The election date may not be sooner than the next available date listed in this subsection for which the filing deadline may be met and may not be later than the first regular district election following the 40th day after the date of the order calling the election.

(2) In a district that does not hold regular district elections, if an initiative or referendum petition contains the required number of verified signatures, the election on the district measure shall be held at the next available date listed in subsection (1) of this section for which the filing deadline may be met.