Combine morsels and sweetened condensed milk in large, microwave-safe dish. Microwave on HIGH (100%) power for 1 minute; stir until smooth.
Spread into prepared baking pan. Place preserves in a small, microwave-safe dish. Microwave at 10 second intervals until slightly warm and easy to stir. Pour evenly over fudge. Use a knife to create a marble effect, being careful to not cut foil. Refrigerate for 4 hours or overnight. Lift from pan. Cut into 36 pieces. Store in refrigerator.