Using a cast iron skillet, add the bacon and garlic. Place it directly on the grill about 225 degrees (107c). The bacon fat will render (melt) providing the moisture for the garlic to cook. The garlic will take awhile depending on how hot your grill is and if you have a “Hot Spotâ€.Stir the garlic every now and then to keep from sticking. After an hour or so the garlic should be getting soft. Stir in the onion. I like them just as they are, still a little crisp. About 30 minutes, again depending on your grill.