In a large skillet, heat the olive oil over medium heat. Add the diced sweet onion and diced red bell pepper. Sauté for about 5 minutes until softened.
Stir in the minced garlic and cook for an additional 1-2 minutes, being careful not to burn it.
Add the Italian sausage to the skillet, breaking it apart as it cooks for about 7-10 minutes until browned.
Stir in the dried oregano, and season with salt and pepper to taste.
Pour in the crushed tomatoes and stir to combine. Bring to a simmer and reduce heat to low. Let cook for about 15-20 minutes.
Adjust seasoning if necessary. Serve over pasta or as desired.
