In a large skillet over medium heat, add breakfast sausage and cook for about 6-8 minutes until browned and fully cooked. Transfer to a plate, leaving the drippings.

In the same skillet, add diced onions and diced bell peppers, sautéing for 4-5 minutes until softened. If necessary, add butter or oil to prevent sticking.

In a large mixing bowl, whisk together eggs, milk, salt, and pepper for about 2 minutes until fully combined and slightly frothy.

Grease a 9x13-inch baking dish and layer in bread cubes evenly at the bottom.

Sprinkle the cooked sausage, sautéed onions and bell peppers, and shredded cheese evenly over the bread cubes.

Carefully pour the egg mixture over the layered ingredients. Use a spatula to gently press down on the bread cubes.

Preheat your oven to 350°F (175°C) and bake the casserole for 40-45 minutes until golden-brown on top.

Let the casserole cool for about 5 minutes in the dish before cutting into portions. Serve warm garnished with fresh herbs.