Cook macaroni according to package instructions; set aside.
While pasta is cooking, heat oil in a large, deep skillet. Add onion, peppers and garlic plus a pinch of salt and pepper and saute until tender, about 5-6 minutes.
Add ground beef and oregano to the pan. Cook until beef is browned through, using a wooden spoon to break into bite-sized pieces. Continue until beef is golden brown, about 8-10 minutes. Stir in tomato sauce and diced tomatoes and heat until cooked through. Check for seasoning and adjust accordingly.
Add pasta to the pot and stir once more. Garnish with parmesan cheese and basil before serving.