Grill first 3 ingredients, covered with grill lid, over medium-high heat (350° to 400°) 8 to 10 minutes or until tender, turning occasionally.
Cut corn kernels from cobs. Coarsely chop onion and red bell pepper halves.
Combine grilled vegetables, tomato, and next 7 ingredients in a large bowl; cover and chill 2 hours or up to 2 days. Serve with chips, grilled chicken, fish, or beef. Garnish, if desired.