Bring a large pot of salted water to a boil. Add 12 oz rigatoni pasta and cook until al dente according to package instructions, usually about 10-12 minutes. Drain and set aside.
Heat 2 tbsp olive oil in a large skillet over medium-high heat. Add 1 lb steak pieces and sear until browned on all sides but not fully cooked through, about 3-4 minutes. Remove steak from skillet and set aside.
In the same skillet, add the diced onion and bell pepper. Cook until softened, about 5 minutes. Add 3 cloves minced garlic and cook for another minute until fragrant.
Lower the heat to medium. Pour in 1 cup heavy cream, stirring to deglaze the pan and incorporate the browned bits. Stir in 1 cup crumbled blue cheese, 1 tsp dried oregano, 1 tsp salt, and 1/2 tsp black pepper. Cook gently until the cheese melts and the sauce thickens slightly.
Return the steak to the skillet with the sauce, then add the cooked rigatoni. Stir gently to coat the pasta and steak evenly with the creamy blue cheese sauce.
Transfer the mixture to a greased baking dish. Sprinkle 1 cup shredded mozzarella cheese evenly on top.
Preheat your oven to 375°F (190°C). Bake the rigatoni bake for 15-20 minutes, or until the cheese is melted and golden brown.
Remove from oven and sprinkle with 1/4 cup chopped fresh parsley for a pop of color and freshness. Serve hot and enjoy!