Definitely depends on the restaurant. Most places, even if they say they're healthy, use the cheapest ingredients they can get away with. They are running a business after all.
My hubby and I meet friends weekly for "All You Can Eat" Wings at a local place, but I no longer get the wings. The oil they are fried in upsets my stomach. I can barely wait an hour after the first round of wings before I need a bathroom. It's definitely the oil doing it, as I make sure to get a "good" wing sauce. I now get a salad topped with grilled chicken and use the wing sauce as a dressing. No digestive issues with this fix.
My favorite restaurant is Carrabba's. They are on the pricey side, but I think it's worth it for the higher quality food. I avoid the bread basket and steer clear of the pasta/pizza. They make everything from scratch and we always ask for the same waiter who knows I'm on a different eating plan. I'll ask him about specific ingredients and they have a big poster that he references in the back that tells him every single ingredient in each dish. I've never had a problem eating there (except that it's hard to resist the breaded calamari!).