In a medium skillet on the stove top cook the ground beef, onion and garlic until the ground beef is cooked through and crumbled. Drain off the excess cooking fat.
Add the cooked ground beef, onion and garlic mixture to the bottom of a 6.5 quart or larger slow cooker. Add the Rotel diced tomatoes, drained corn, marinara sauce, Italian seasoning and salt and pepper.
Give everything a quick stir and cover and cook for 6 hours on LOW or 3 hours on HIGH.
About 30 minutes before the end of the cooking time (or before you are ready to serve) bring a large pot of water to boil on the stove top and cook the macaroni pasta according to the package directions until they are al dente (about 7 minutes). Drain the pasta and carefully add the cooked pasta into the slow cooker and stir to coat all the pasta with the sauce mixture.
If you don’t have enough room in the slow cooker, pour the sauce and pasta into 1 large mixing bowl and mix in that to prevent making a mess.
Add shredded cheddar cheese right before serving and enjoy!