1. Add the vegetable oil to a dutch oven set over medium heat.  Once the pan is hot add the stewing beef (working in batches if necessary) and brown on all sides.
2. Add the onion, carrot, celery and garlic. Cook for another 4-5 minutes until the vegetables are soft. Stir in the dried oregano.
3. Add the beef broth, scraping any brown bits from the bottom of the pan. Stir in the crushed tomatoes and stir to combine. Season with salt and pepper. Bring to a simmer, cover and cook for about 2 hours, stirring occasionally, until the beef is tender.
4. Use two forks to pull the beef apart. Taste for seasoning and adjust accordingly. Turn off the heat and cover while you make the pasta.
5. Place a large pot filled with water over high heat. Add the rigatoni and stir for about 15 seconds. Cook according to the package directions.
6. Transfer the cooked pasta to the braised beef, bringing a little pasta water along to help thin out and enrich the sauce. Toss to combine. Add the parmesan cheese and toss.

Serve garnished with more cheese.