HEAT oven to 400°F.
MIX milk, dressing and flour in large microwaveable bowl. Microwave on HIGH 2 to 3 min. or until sauce is thickened, stirring after each min. Stir in cheese; microwave 1 min. Mix until well blended. Add turkey, mixed vegetables and onions; toss to coat. Spoon into 9-inch pie plate; smooth surface.
PLACE crust over filling; flute edge and seal to rim of pie plate. Cut several slits in crust to permit steam to escape. Place on baking sheet.
BAKE 30 to 35 min. or until crust is golden brown. Let stand 10 min. before serving.