Directions:

Set a large skillet over medium heat; coat it with nonstick spray or a little olive oil.

Place sausage in the skillet and break it up with a spatula. Stir in the rosemary and brown the sausage for about 6 or 7 minutes.

Meanwhile, (if your skillet isn't large enough to fit both sausage and veggies in one skillet), set a second skillet over medium heat, again coated with nonstick spray or a bit of olive oil.

Add the peppers, mushrooms, spinach, onion, garlic, and a sprinkle each of salt and pepper. Stir and cook the veggies down until they are tender, about 6-8 minutes.
Set sausage and veggies aside.

Generously grease a 9×13-inch baking pan. Break the bread slices into pieces and place in the pan in an even layer.

In a large bowl, whisk together the eggs, milk, and 1/4 cup of the shredded cheese.
Pour half of this egg mixture over the bread. Top with the sausage and vegetables, then the remaining egg mixture and remaining 1/4 cup cheese. Add a sprinkle of salt and pepper on top.

Cover casserole with plastic wrap or aluminum foil and refrigerate for 2 hours or overnight – or up to 1 day. Allow it to come to room temperature before baking.

Preheat the oven to 375°F (191°C). Bake the casserole, uncovered, until the top is golden, the edges are crisp, and a toothpick inserted in the center comes out clean– about 40-45 minutes, or if you like yours on the super crisp side, bake it for around 45-50 minutes. Allow to cool for 10 minutes, then slice and serve. It tastes great with hot sauce on top.

Leftovers keep well in the refrigerator for up to 5 days. Reheat in the microwave as desired.

Make Ahead & Freezing Instructions:
Obviously this is a make ahead recipe! However, you can brown the sausage and cook down the veggies up to 2 days in advance– simply put the two in an air-tight container in the refrigerator until ready to use in the recipe.

Also, you can freeze this breakfast casserole. Prepare through step 5, then cover the casserole with plastic wrap, then a layer of aluminum foil. Freeze for up to 3 months. Allow to thaw overnight in the refrigerator. Bring to room temperature, then continue with baking instructions above.

The onion, garlic, salt, pepper, and cheese are key to great flavor! Don’t leave them out.

Variations:

Sausage: Replace sausage with ground turkey, ground beef, ground chicken, diced ham or cooked shredded chicken.

Vegetarian Option: Omit the meat. Add an extra cup (or so) of veggies in its place.

Cheese: I usually use shredded pepper jack cheese; other varieties that work really well for this breakfast casserole are mozzarella, smoked gouda, swiss, and cheddar.