Preheat the oven and prepare the baking pan. Preheat the oven to 350° F. Spray the baking pan with nonstick cooking spray.
Sautee the onions. In a small skillet over medium heat, sautee onions in olive oil until golden brown. This will take about 10-15 minutes.
Steam the broccoli. Meanwhile, place broccoli into a microwave-safe dish, covered with 1-2 tablespoons of water, and cook for 2-3 minutes or until bright green and softened.
Whisk the egg mixture. In a medium-sized mixing bowl, add eggs, milk, garlic, and salt and pepper. Whisk until blended.
Layer strata in baking pan. Lay the bread on the bottom of the baking pan. Top with steamed broccoli, sliced tomatoes, and sauteed onions. Pour egg mixture over the vegetables. Top with shredded cheese. With a spatula, gently push down to get the egg mixture covering most of the ingredients.
Bake. Bake for 50 minutes or until the eggs are set and the cheese is melted and bubbly. Serve hot.