On the West Coast I guess it would be Olive Garden or Maggianos. Maybe AG can think of other chain Italian restaurants.
Maggiano's is alright. Forget about Olive Garden
The best chain restaurant here in California would have to be Filippi's. Good food. Good pizza. Sauce/gravy tastes authentic. They are down in the Escondido, San Diego area and I'm pretty sure there are a couple up north. We eat at the one in San Diego's Little Italy.
A lot of east coast transplants including myself like Panera. It's not an Italian restaurant but it is a good place to get a sandwich on decent tasting bread.
