The four people were found dead Wednesday after a caller told police about an alarming post on a social network.
All four had been shot. An autopsy is planned Thursday.
Police say 37-year-old Randall Engels is suspected of killing 35-year-old Amy Engels and their school-age children.
Capt. Jeff Kosmicki said the family had lived for several years in the town of Dundee in one of Oregon's prime wine regions. He didn't identify the children.
