Preheat the oven to 350°F.
Put the bread into a large mixing bowl and add the milk. Press the bread into the milk and let sit until the milk is absorbed and the bread is soft, about 15 minutes.
Heat 3 tablespoons of the olive oil in a large (12-inch) skillet over medium-high. Add the ground beef, and cook, stirring, until lightly browned, about 1 minute. Add the sausage and cook, stirring until browned, about 3 minutes. Add the onions, bell peppers, celery, and bay leaf. Season with the salt, crushed red pepper, and black pepper.
Cook, stirring occasionally, until the vegetables are slightly softened, about 4 minutes. Add the garlic and cook, stirring, until fragrant, about 30 seconds.
Transfer the meat mixture to the bread mixture and stir to mix well. Add the eggs and parsley and stir well to blend. Remove the bay leaf and discard.
Grease a 9 x 13-inch (3 quart) shallow baking dish with the remaining tablespoon olive oil. Pour the mixture into the prepared pan and spread evenly with a rubber spatula.
Bake until bubbly and golden brown, about 1 hour. Remove from the oven and serve warm.