The Travelin Man
This would be most of the way to Portland, but before you cross the Oregon border, one place that I like is in Vancouver, WA. It is called Yankee Pot Roast. I thought that it was reviewed on this site or in a previous edition of ‘Roadfood’, but I cannot find the review online any more.
As you would expect, the pot roast dinner is excellent, as are the biscuits to sop up the roast juices/gravy.
I may have read on another site that this place is now closed. I would try to research some before making that your destination. Maybe one of the Portland locals can confirm/deny. If it is closed, it will be missed by me.