Divide your meatloaf mixture into two portions. One portion should be about 1/2-3/4 of your mixture and the second portion will be the remaining mixture.
From the larger portion make twelve meatballs about the size of a golf ball. Place the meatballs in the muffin tin.
Press the meatballs into the muffin tin to make a shell. Make sure that there is a good size hole and that the meat goes up the sides of the tin.
Fill the hole with some of the onion, green pepper and cheese.
Lastly, make a lid out of the remaining meatloaf mixture. Be sure to seal the lid to the meatloaf mixture that is already in the tin.
Bake at 350 degrees for approx. 45 minutes.
Note: I have played with the meat mixture and found that ground turkey or pork work just as well as the ground beef. Also, I have played with the vegetables and the cheese. This is a very kid friendly dish.