I recently spent my birthday in the Methow Valley and did some serious research about where to eat on the special night. Unfortunately, it appears the Twisp/Winthrop/Mazama stretch is pretty bleak for good vegetarian food.
I initially got really excited about this: http://www.winthroptipidinners.com/, an unusual (and not corny/cooperate/tourist trap, as the name might make you think) restaurant developed as a life dream by a local woman that revolves around eating artfully prepared, healthy, traditional (local as possible) Native American foods while in a beautiful tipi. In the winter time, there is fire and candle light and and animal skins to keep everything warm. The proprietress, Suekii, cooks everything in a nearby kitchen and brings it via hand held wagon to her hungry guests. I spoke to Suekii about what she does for vegetarians (no bison steak for this birthday gal), and it all sounded wonderful... hummus and pickled asparagus, stuffed squash, emmer farro, etc. But it turned out that the tipi was already fully booked (it only holds 8) on the night of my birthday.
There are other fancy type options in the area, including the Sun Mountain Lodge and the Arrowleaf Bistro, but these have really limited vegetarian entrees that are priced at meat prices. No thank you.
So I went to the Twisp River Pub, where I knew there were decent vegetarian options to be had. My dining companion and I split two things: the Asian salad and a veggie burger with fries.
Based on the menu description, I had hoped that the Asian salad (with rice noodles) would be similar to the contents of a Vietnamese bun. Turned out the noodles were more of a garnish, and the salad was mostly green. I ordered it with fresh tofu (instead of fried), which was possibly a mistake, because it came fully unmarinated (rather than in the sesame marinade the menu describes).
The pub-made veggie burger was tasty, and the fries were excellent.
For my birthday dessert, I ordered a warm walnut brownie with vanilla ice cream. It was delicious.