Grand Coulee Dam food?
I haven't been to the dam itself, but my family stopped for lunch in Coulee City a couple of years ago. I don't remember what the place was called but it was a perfectly nice American diner with fun waitstaff and a very satisfactory hot roast beef sandwich. Our usual stop on the way out to Spokane is a cafe in Wilbur that does fantastic reubens, but that's a bit out of your way.
What route are you taking to get out there?