Preheat oven to 375° F. Grease a 9x13-inch baking dish and set aside.
Bring a large pot of salted water to a boil. Once boiling, stir in the rigatoni and cook for the minimum cook time listed on the package until al dente; then drain and set aside.
Heat olive oil in a Dutch oven or large skillet over medium-high heat. Add chopped onion and cook until softened, about 2-3 minutes, stirring occasionally before adding ground beef or sausage.
Cook the meat until browned while breaking it apart with a spatula; drain excess grease if needed before adding minced garlic for about 30 seconds until fragrant.
Add marinara sauce, Italian seasoning, and black pepper into your skillet mixture; bring to simmer then reduce heat to low cooking at low simmer for 10 minutes stirring occasionally allows flavors to meld beautifully.
Remove from heat; stir in ¼ cup of grated Parmesan followed by gently mixing in cooked rigatoni before transferring everything into your greased baking dish ensuring even distribution throughout before sprinkling mozzarella over top along with remaining Parmesan cheese followed by oregano.