
Preheat oven to 350℉ (175℃).
In a large, deep skillet, cook sausage over medium-high heat for about 10 minutes until they're no longer pink. They'll be crumbly and evenly browned.
Drain well using a colander to remove excess grease and set aside to cool.
Melt butter in the skillet, and add onions, bell peppers, and garlic. Cook over medium heat until tender, 3-5 minutes. Set aside and let cool.
In a large bowl, whisk eggs and milk. Stir in the sausage and sauteed vegetables. Add shredded cheese, Creole seasoning, salt, baking powder, and melted butter. Mix until thoroughly combined.
Lightly grease a 9×13-inch baking dish and arrange the cubed bread along the bottom. Pour the sausage and egg mixture over the bread, spreading out over the bread.
Bake it for 40-45 minutes or until golden brown. The casserole will be firm, and a knife inserted in the center will come out clean. Let it rest for about 10 minutes before serving. Enjoy hot!