Heat a large nonstick skillet over medium-high heat. Add onion slices (keep slices intact), cook 3 minutes on each side or until browned.
Combine milk, salt, thyme, pepper, and eggs in a large bowl, stirring with a whisk. Add the bread cubes and 1 cup cheese, and toss mixture well. Place the bread mixture in a baking dish coated with cooking spray. Arrange onion slices on top of bread mixture. Sprinkle with 1/2 cup cheese. Bake at 425 degrees for 25 minutes or until set and golden. Serves 8. (Cooking Light)