1.In a skillet, heat the olive oil on medium heat.
2.Brown the ground beef and onion.
3.Add garlic, salt, pepper, and Italian herb seasoning. Cook until the meat is no longer pink. Leave a few tablespoons of 4.liquid in the pan to keep the meat moist.
5.Spray the slow cooker with non-stick spray. Pour half of the marinara sauce into the bottom of the slow cooker.
6.Layer half of the frozen ravioli on top of the sauce.
7.Add the cooked ground beef mixture evenly over the ravioli.
8.Layer the remaining ravioli on top of the meat.
9.Pour the remaining marinara sauce over the ravioli.
10.Sprinkle the shredded mozzarella cheese evenly on top.
11.Place the lid on the slow cooker and cook on LOW for 4 hours.
12.Serve hot and enjoy!