Remove giblets and necks, if necessary. Rinse chickens with cold water; pat dry. Place each chicken in a large zip-top plastic freezer bag.

Whisk together oil and next 5 ingredients. Pour evenly over chickens. Seal bags, and chill, turning occasionally, 8 hours. Remove chickens from marinade, discarding marinade.

Using a can opener, carefully remove lids from cans of ginger ale. Remove one-fourth ginger ale from each can, and reserve for another use, leaving remaining ginger ale in can. Place cans in a lightly greased large roasting pan. Place each chicken upright onto a ginger ale can, fitting can into cavity. Pull legs forward to form a tripod, allowing chickens to stand upright.

Bake, uncovered, at 325° for 1 hour and 40 minutes or until a meat thermometer inserted into thigh registers 170° and chickens are golden brown. Let stand 10 minutes; carefully remove cans before serving. Garnish, if desired.