In a large skillet, heat the olive oil over medium heat. Add the Italian sausage and cook until browned on all sides, about 8-10 minutes.

Remove the sausage from the skillet and set aside. In the same skillet, add the sliced bell peppers, onion, and garlic. Sauté until the vegetables are tender, about 5-7 minutes.

Slice the cooked sausage into bite-sized pieces and return it to the skillet with the vegetables. Add the oregano, red pepper flakes, salt, and black pepper. Stir to combine and cook for an additional 5 minutes.

Serve hot, either on its own or with crusty bread or over pasta.