Preheat the oven to 425 degrees. In a large skillet, heat the olive oil over medium heat. Add the onions, green pepper, and sausage to the pan and cook until onion is soft and sausage is fully browned, about 6-7 minutes. Remove to a plate, leaving the oil behind.

Add the mushrooms to the skillet. Allow to cook for a few minutes undisturbed, then toss and continue to cook until softened, another 2-3 minutes. Sprinkle with salt. Add the sausage, peppers, and onion back to the pan and stir. Drain off any excess oil.

Place about 3/4 of the sausage mixture at the bottom of a 9 x 13 inch pan followed by all of the marinara sauce. Layer 10 pepperonis on top. Then layer on half of your shredded cheese (about 1 1/2 cups).

Scatter the garlic bread cubes on top followed by the rest of the pepperonis and sausage. Cover with the remaining 1 1/2 cups cheese. Place in the oven and bake for 15-18 minutes or until garlic bread is toasted and cheese is melted.