Coat bell peppers and onions with cooking spray. Place bell peppers and onions on grill rack coated with cooking spray; grill 15 minutes or until peppers are blackened, turning occasionally. Place peppers in a zip-top plastic bag; seal. Let stand 15 minutes.
Chop onions into 1-inch pieces; place in a large bowl. Peel and slice peppers into 1/2-inch strips; add to onions.
Combine the oil, mushrooms, and asparagus; toss well to coat. Place mushrooms and asparagus on grill rack; grill 3 minutes on each side or until tender.
Chop mushrooms into 1-inch pieces; add to onion mixture. Slice asparagus diagonally into 1 1/2-inch pieces; add to onion mixture. Drizzle 1/3 cup Chile-Garlic Vinaigrette over mixture; toss to coat.
Note: Store cooked vegetables in refrigerator for up to 3 days.