|Preheat the oven to 350 degrees. In a baking dish, toss together 2 of the minced garlic cloves, 2 tablespoons of olive oil and the bread cubes. Bake in the oven, stirring once, for 8 to 10 minutes, or until lightly toasted. Set aside.|
In a skillet over medium heat, add 1 tablespoon of olive oil and the onion, peppers and squash. Saute the vegetables for 6 to 7 minutes. Season with salt and pepper. Set aside.
In the same skillet, sauté two garlic cloves in 1 tablespoon of oil. Add mushrooms and sauté for 6 to 7 minutes until softened. Season with salt and pepper.
Place bread cubes into a lightly oiled 9 x 13 inch baking dish. Pour vegetable mixture on top. Place spinach leaves over top of vegetable layer. Pour mushrooms over top of spinach leaves. Spread cheeses on top of vegetables.
In a large bowl, whisk together eggs and milk. Pour egg mixture over cheese layer. Place halved grape tomatoes on top. Cover with foil and refrigerate overnight.
Remove from fridge and let stand 30 minutes before baking. Bake at 350 degrees until set, about 40 to 50 minutes. Let stand for 10 minutes before cutting into squares to serve.