Grease a 9×13-inch baking dish or any 3 to 4-quart oven-safe casserole dish.

Arrange the cubed bread evenly across the bottom of the dish.

Heat the olive oil in a large skillet over medium heat.

Add the halal beef sausage and rosemary or Italian seasoning, if using. Break the sausage into small pieces as it cooks.

Stir in the onion, garlic, bell peppers, mushrooms, and spinach. Cook for 5–6 minutes until the vegetables soften and the sausage is fully cooked.

Spread the sausage and vegetable mixture evenly over the bread cubes.

In a large bowl, whisk together the eggs, salt, black pepper, milk, and shredded cheddar cheese.

Pour the egg mixture evenly over the sausage and vegetables.

Sprinkle a little extra salt and pepper over the top if desired.

Cover the casserole tightly with foil or plastic wrap and refrigerate for at least 30 minutes or up to 24 hours.

When ready to bake, remove the casserole from the refrigerator and let it sit at room temperature for 10–15 minutes while the oven preheats.

Preheat the oven to 375°F (191°C).

Bake uncovered for 40–45 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.

Let the casserole cool for about 10 minutes before slicing.

Garnish with chopped parsley or green onions and serve warm.