Split each onion down the middle and remove the inner layers, setting the 2 outermost layers to the side. Do this four times so that you have 8 outermost layer sections to work with later.
Dice the rest of the onions and the mushrooms. Mix these two ingredients, along with all the others (except for the bacon) into the ground beef.
Now form your ground beef mixture into four equal-sized balls.
Gently place each meatball into two of the outermost onion layers, so that you form a stuffed onion.
Finally, cover in a thick layer of bacon by wrapping bacon slices around each onion. Toothpicks can help make this process easier!
Now the stuffed onions are ready to be grilled, but be sure not to place them directly over the charcoal. Feel free to brush them with a little BBQ sauce! Grill the onions for about 40 minutes and just before serving, place them directly over the charcoal to ensure the bacon is extra crispy!
