We had the good fortune to vacation in the Moab area, staying in Castle Valley, and with a side trip to Bluff. Here's a report of where we ate:
There are two restaurants in Castle Valley, where we were staying.
--Cowboy Grill. My steak had an awful flavor and was overcooked. My DH's trout was mediocre. The spinach salad with beets and goat cheese was served with slices of canned beets. Not recommended.
--Sorrel River Grill. The food was excellent (flatbread with duck confit and cherries, pork belly posole, pasta with wild mushrooms) but it was extremely pricey. A fellow diner who knows wine stated a bottle that usually goes for $80 was on the menu here for $320. The service was incompetent, but to be fair it was my waiter's 2nd day on the job.
Overall, it's worth making the beautiful 30 minute drive to Moab to eat.
Milt's: tiny burger joint, but you can eat outside. Fries were soggy and oily--stick to the onion rings. You go there for the shakes--amazing. We returned later in the trip just for those coffee shakes.
Paradox Pizza. Good, one oddity was they burned my pizza and asked if I wanted a replacement.
Miguel Baja: Excellent lamb enchiladas, succulent morsels of lamb surrounded by a green sauce. DH liked his portobello fajitas.
Desert Bistro: we liked it so much we cancelled other reservations so we could return. First night I had a bison tenderloin, perfect, DH had fantastic mushroom ravioli. Appetizer was slices of seared ahi crusted with white and black sesame seeds. Second night DH had a Hawaiian fish that was excellent, I had lamb that was very good. both of us had a citrus-cumin salad that was quite fine. Highly recommended.
Bluff: we made a 100 mile detour to Bluff to see cliff dwellings. For a town of 400 people, they had some good food!
Twin Rocks Cafe: the only restaurant open year round, had a diner feel. I had an excellent Thai chicken sandwich on fry bread, and DH had a "smokestack" burger with a bit of everything--very good. Much better than my expectations.
Comb Ridge: I had a smoked salmon salad and DH had fish and chips which were lighter than he expected. Very nice. Functions as an espresso bar during the day.
Hope this helps!