At least three locations in ORD's Terminal 3 (food court, H concourse, K concourse) - but then, with its world headquarters in nearby Oak Brook, McDonalds qualifies as a
local food vendor at ORD
Myself, I prefer Burrito Beach, both for the food and because they serve Diet Dr. Pepper ^ (I also look forward to the soon-to-open Rick Bayless/Frontera outlet in T3).