Cut stew meat into bite sized pieces. Thoroughly cook stew meat in large pot.
Split the loaves into halves and remove some of the bread from the top half (so the bread is not so thick). Spread Kraft Mayonnaise and sprinkle Kraft Cheese on both sides of the loaves. Top with stew meat.
Bake at 375°F until the cheese is melted and the loaves are toasted. Add lettuce, tomatoes, and onions. Replace the top half of the loaves and then cut in half.