To a large skillet over medium heat, add the ground beef and season (salt, pepper, onion, Montreal steak seasoning). Cook the meat, breaking it apart until no longer pink.
    Turn the heat down and pour in the sauce. Let simmer for a few minutes.
    Spray the bottom of a 6 quart slow cooker with non-stick spray and then spoon in approximately 1 cup of meat sauce into the bottom of the slow cooker.
    Top with half of the ravioli, half of the remaining sauce, and a handful of cheese. Repeat with the remaining ingredients, finishing with cheese on top, making sure to tuck the ravioli under the sauce and cheese.
    If starting with frozen ravioli, cover and cook on LOW for 3-4 hours.
    If starting with thawed/fresh ravioli, cover and cook on LOW for 1-2 hours.