For cookies, cream margarine with peanut butter. Mix in sugar, then beat in eggs and milk. Stir in baking soda, oats, and flour.
To Make Filling: Combine raisins, water, and lemon juice. Heat until nearly boiling. Mix sugar with cornstarch; add enough (cold) water to make a paste. Stir into raisin mixture and heat until clear.
Shape dough into walnut-sized balls. Place on a greased cookie sheet. Using your thumb, indent the center of each ball, making a fairly good-sized hollow spot. Fill with about a teaspoon of filling. Bake at 375 degrees F (190 degrees C) for about 10-12 minutes.