Spray 11x7-inch microwavable dish with cooking spray. In large bowl, stir together mayonnaise, eggs, flour and salt; stir in squash mixture and cheese. Spoon mixture into baking dish. Cover tightly with microwavable plastic wrap, folding back one edge or corner 1/4 inch to vent steam. Microwave on High 10 minutes or until set; let stand 10 minutes.