a) ORS 471.130 requires a licensee or permittee to verify the age of a person who wants to buy or be served alcoholic beverages when there is "any reasonable doubt" that the person is at least 21 years old. The Commission requires a licensee or permittee to verify the age of anyone who wants to drink alcoholic beverages, or is in an area prohibited to minors, if there is reasonable doubt that the person is at least 21 years old. "Reasonable doubt" exists if the person appears to be under the age of 26;

It's not a big deal, however, it seems the ORS addresses a "minor" in the context of legal alcohol consumption as someone under the age of 21.  That "18" comes into play relating to consensual sex.