Grease 13x9-inch pan. Place half of the crackers in bottom of greased pan.
In medium saucepan, combine sweetened condensed milk, brown sugar, butter and 1/4 cup milk. Cook over low heat until butter is melted, stirring frequently. Increase heat to medium-high; bring to a boil. Boil 5 minutes, stirring constantly. Remove from heat. Stir graham cracker crumbs into caramel mixture.
Pour half of caramel mixture over crackers in pan. Arrange remaining crackers over caramel. Top with remaining caramel mixture.
In small saucepan, heat chocolate chips and 2 tablespoons milk over low heat until chocolate is smooth, stirring frequently. Stir in peanut butter. Spread over bars. Refrigerate 30 minutes or until set. Cut into bars.