Heat oven to 400°F. Spray 9-inch glass pie plate with cooking spray.
Sprinkle ham, pineapple and onions in pie plate. In medium bowl, stir baking mix, milk, eggs and mustard until blended; pour over ham mixture.
Bake uncovered about 25 minutes or until knife inserted in center comes out clean. Sprinkle with cheese. Bake 3 to 4 minutes longer or until cheese is melted.