Oregon has one of the worst voter-registration online systems in the country however, a date of birth + residency will give access to party registration of the individual, alongside some other information I believe.
IIRC Oregon is one of the states that sells a big CSV of every registered voters name, address, and party affiliation. So really all they're doing is competing with their own business
Quick edit: It's $500 to get data for everyone in the state, but there might be an extra fee if you want to know when they voted
