Heat a large 12-inch oven-safe skillet over medium-high heat and add smoked sausage, cook until brown. Add garlic, onion and bell pepper. Lower heat to medium and stir until vegetables are soft, about 5 minutes.
Stir in cooked tortellini, oregano, marinara sauce and one cup of cheese. Top with remaining cheese. Bake in the oven for about 10 minutes until cheese is melted and bubbly.