Grilled Marinated Vidalia

2 large vidalia onions, peeled
1/2 cup olive oil
1/2 cup balsamic vinegar
1 tsp minced fresh thyme, or 1/2 tsp dried thyme
1/2 tsp salt
1/2 tsp pepper

Slice onions horizontally into large circles. Lay the 10-11 slices flat on cookie sheet with rim. Whisk all other ingredients together in mixing bowl and pour over slices. Refrigerate. Marinate for 8 hours or over night. While burgers are cooking on the grill, place slices in an aluminum foil bundle on top rack of grill. Cook for 20-30 minutes until tender. Serve hot with burgers.