HEAT oven to 350°F.
BLEND tomatoes and 1/4 cup dressing in blender until smooth. Heat small heavy skillet on medium-high heat. Brush tortillas with remaining dressing. Add, 1 at a time, to skillet; cook 2 to 3 min. or just until warmed.
ARRANGE 6 tortillas on bottom of 13x9-inch baking dish sprayed with cooking spray. Cover with layers of half each of the chicken, peppers, tomato sauce and cheese; top with remaining tortillas, chicken, peppers and tomato sauce. Cover.
BAKE 30 min. or until heated through, uncovering and topping with remaining cheese for the last 5 min.