A nice little lunch spot at the Fossil Rim Wildlife Center. It has a rather limited menu made up mostly of sandwiches and burgers, but the ones we had (grilled chicken sandwich, reuben sandwich and veggie burger), were very tasty and well above the type of fare you'd expect at your average "tourist trap"-type eatery. I've had grilled chicken sandwiches and reubens at standard sit-down restaurants that weren't even half as good.
As the name implies, the Overlook Cafe has a spectacular view of part of the Fossil Rim Wildlife Center (it overlooks a valley around the giraffe barn where I noticed a lot of zebras and fallow deer hanging around; it's a ways off, though, so it might be worthwhile to bring your binoculars). Also has several hummingbird feeders and other bird feeders, so lots of birds flitting around to watch.
And you don't have to be visiting Fossil Rim to eat at the Overlook. Drive a ways past the Fossil Rim Wildlife Center's main entrance and watch for signs to the Overlook Cafe (you'll end up taking a couple of right turns to get to the cafe's parking lot).