We stayed in Mammoth Hot Springs in Yellowstone National Park, 5 miles from Gardiner. The food in Yellowstone leaves a lot to be desired; granted, they're trying to feed a lot of people in a remote area.
We were thrilled when we discovered that it's cheaper and easier and tastier to drive the five miles to Gardiner and eat at the Yellowstone Grill rather than wait in line at the Mammoth Grill or the Mammoth Diner in the park (the park restaurants had long lines, slow service, and expensive food that wasn't very good.)
We found the Yellowstone Grill to have great food for a good price, especially compared to park prices. The staff was friendly and the atmosphere was nice. They have free wi-fi, which I used to check email since I couldn't get it in the park.
We had lunch there one day, and breakfast another day. The food was really good. We'll remember this place and come back to it!