I recently visited a Bonefish Grill Restaurant...it was FANTASTIC. I went to the location in Venice, Florida. They have a separate gluten free menu. I had mussels as an appetizer and the shrimp and scallops as my main meal. They offer quite a few options. They aren't cheap, but I didn't think they were overly expensive either.
Here is a link to their GF menu:
The only Iowa Location is in West Des Moines. They do have a few in Illinois near Chicago.