In a large mixing bowl, cream margarine (butter) and flour with a pastry cutter and set aside.
In a small bowl, dissolve powdered milk and garlic powder in water and wisk in beaten egg.
Make a well in the flour mixture and gradually stir in egg mixture until well blended.
Knead dough on floured surface, about 3 to 4 minutes, until dough sticks together and is easy to work with.
With a rolling pin, roll dough to between 1/4" to 1/2" thickness.
Cut with a cookie cutter and place on lightly greased baking sheet.
Bake 50 minutes at 325°F.
Cool on rack until hard and store at room temperature, in a container with a loose fitting lid.