Preheat the oven to 425°F (220°C).
In a large skillet, heat olive oil over medium heat.
Add the Italian sausage, breaking it up with a spoon, and cook until browned and cooked through, about 7-8 minutes. Remove sausage from skillet and set aside.
In the same skillet, add diced green bell pepper, diced onion, and sliced mushrooms. Cook until vegetables are tender, about 5 minutes. Remove from heat.
In a deep dish pizza pan or a 12-inch round cake pan, layer the toppings starting with half of the shredded mozzarella cheese evenly spread on the bottom.
Add the cooked Italian sausage evenly over the cheese layer.
Spread the cooked vegetables evenly over the sausage.
Sprinkle dried oregano, dried basil, and garlic powder evenly over the vegetables.
Add the remaining shredded mozzarella cheese over the herbs and vegetables.
Pour the chunky tomato sauce evenly over the top of the cheese layer, covering the entire surface.
Place the deep dish pizza in the preheated oven and bake for 35-40 minutes, or until the crust is golden brown and the sauce is bubbly.
Remove from oven and let the pizza rest for 5 minutes before slicing and serving.