Hi Pat,
I don't know if this is the preferred way but it's how I go as I don't mind riding higher traffic roads with bike lanes: Murray, Scholls, Roy Rogers, Hwy 99 to Newberg, St Paul Hwy to Champoeg Rd. Total of 25.6 miles from 185th & TV Hwy, 1,346 total ft. of climb, with a max elevation of less than 500 ft. If you're up for more of a climb on rural no shoulder roads, stay on Scholls to Hwy 219 into Newberg, about an 1,100 ft climb over 5 miles.
"It doesn't get any easier. You just go faster" ~ Greg Lemond