Ok - it's no El Charro. But if I had to pick a chain restaurant on campus, I'd go with Chipotle. Especially now that Chipotle isn't owned by McDonald's anymore - I feel better about endorsing them.
Their veggie burrito bowls are very filling and the majority of the ingredients are organic, naturally raised, sustainable, hormone free and sometimes, even locally grown! It is truly Food With Integrity, like their ads claim. And anyone who goes to Qdoba (greasy barf) is out of their mind.