Cut poblano chiles and red peppers in half lengthwise; remove and discard seeds and membranes. Place, skin side up, on a baking sheet; flatten with palm of hand. Cut squash in half lengthwise; coat squash with cooking spray. Place squash on baking sheet, cut side down. Broil peppers and squash 5 1/2 inches from heat (with electric door partially opened) 15 to 20 minutes or until peppers are charred. Place peppers in ice water until cool. Broil squash 5 to 10 additional minutes or until charred. Place squash in ice water until cool. Remove peppers and squash from water; peel and discard skins. Cut into 1/2-inch strips.
Combine vinegar and remaining ingredients in a small bowl; stir well. Combine pepper strips and squash in a bowl; add vinegar mixture, and toss gently. Cover and chill until ready to serve. Serve with a slotted spoon.