Where in southern Oregon? On the coast or inland??
If around Medford, then I5 south to Sacramento, I80 east as far as you want and then head south. If your on the coast, then 101 to CA 20 east to I5 and follow my previous suggestion. If your in eastern Oregon and again depends how far east or south, 395 or I84 to Salt Lake City area where you pich up I80