Both returning burgers offer the same classic combination of ingredients as the original Big Mac (i.e. beef, Big Mac special sauce, lettuce, American cheese, pickles, and onions on a sesame seed bun.) but in varying sizes and proportion.
The Mac Jr. is the smallest of the three and comes with a single patty (of the same size as the Grand Mac, which is bigger than a single patty from the Big mac) and without a middle bun.
The Grand Mac is wider than a regular Big Mac with two beef patties that together weigh about a third of a pound before cooking.
You can find my comparison of the three Big Macs here.
Photo via McDonald's.
