Arrange croutons in a greased 13-in. x 9-in. x 2-in. baking dish. Sprinkle with chilies and cheese. In a bowl, beat the eggs, milk, mustard, salt and garlic powder. Pour over cheese. Cover and refrigerate for 8 hours or overnight.
Remove from the refrigerator 30 minutes before baking. Bake, uncovered, at 350 degrees F for 40-45 minutes or until a knife inserted near the center comes out clean. Let stand for 10 minutes before cutting.