In a large plastic resealable bag, add the chicken and the 1/2 cup salad dressing. Close bag and make sure the dressing coats all of the chicken.
Marinate in the refrigerate for at least 4 hours but not longer than 6 hours.
About 15 minutes before ready to grill the chicken, combine the vegetables in a large bowl and toss with the 1/4 cup salad dressing. Let sit for 15 minutes.
Preheat grill to medium-high heat. Spray a aluminum foil grill pan (with holes) with nonstick spray. If using an aluminum foil pan with no holes, simply poke holes in the bottom of the pan.
Pour vegetables onto prepared pan. Grill vegetables till tender crisp, about 20 minutes stirring occasionally.
Place chicken on grill and cook till done, about 20 minutes turning once.