Make 4 slices across each red onion within a 1/2 inch of cutting through them. Into these incisions, place 1 piece of bacon and 1 slice of garlic. Place each onion in the center of a piece of foil. Repeat with remaining ingredients.
In a small mixing bowl, combine the thyme, vinegar, oil, salt, and pepper. Spoon over each onion. Bring the corners of the foil up over the onion and twist into a tight package. Place on a sheet tray and bake for 1 hour. Remove from oven and allow to cool slightly before removing foil. To serve, heat by fanning on a hot well-oiled grill or in the oven. Serve with a smile.