Cook the pasta in a large pot of salted boiling water until al dente, according to package instructions.
While the pasta is cooking, heat a large skillet over medium heat and add the ground beef, breaking it apart with a spatula.
Add the chopped onion to the skillet and cook until translucent, about 5 minutes.
Stir in the minced garlic and dried oregano; sauté for 1 minute until fragrant.
Pour in the marinara sauce and bring the mixture to a gentle simmer; let it cook for about 5-10 minutes.
Once the pasta is cooked, drain it, reserving some pasta water, and add it directly to the skillet with the beef and sauce.
Mix everything together thoroughly and season with salt and pepper to taste.
Serve hot, garnished with grated Parmesan cheese if desired.