HEAT oven to 375°F.
COOK mushrooms and broccoli in skillet sprayed with cooking spray on medium heat 8 to 10 min. or until broccoli is crisp-tender, stirring occasionally. Remove from heat.
LINE 2-L casserole dish with crust; fold over and crimp edge. Beat eggs, dressing and milk in medium bowl with whisk until well blended. Stir in cooked vegetables, Velveeta and onions; pour into crust.
BAKE 40 min. or until centre is set and top is golden brown. Let stand 10 min. before serving.
