Cook the tortellini according to package directions. Preheat oven to 400 degrees.
Fry the peppers, onions and garlic in a greased pan. We used cooking spray but olive oil would work wonderfully here. Cook these until they soften and brown a bit and then set aside.
Add 1 cup of marinara sauce to the cooked and drained tortellini and stir to combine.
Spray a casserole dish with cooking spray. Scoop in half of the sauced tortellini and add half of the onion, pepper, garlic mixture on top.
Sprinkle with ¾ cup of shredded mozzarella.
Add the remaining tortellini and top that with the leftover veggies and another ¾ cup of mozzarella.
Finally, top with the fresh basil.
Heat in a 400 degree oven for 20 minutes.