MICROWAVE 1 1/3 cups butterscotch morsels, semi-sweet morsels and peanut butter in large, microwave-safe bowl on HIGH (100 percent) power for 1 minute; stir. Microwave at additional 10- to 20-second intervals, stirring until smooth.
ADD pretzels, peanuts and chocolate covered raisins; stir well to coat. Spread into prepared baking dish.
PLACE remaining butterscotch morsels in small, heavy-duty plastic bag. Microwave on MEDIUM-HIGH (70 percent) power for 30 seconds; knead bag to mix. Microwave at additional 10- to 20-second intervals, kneading until smooth. Cut tiny corner from bag; squeeze to drizzle over candy.
REFRIGERATE for 1 hour or until firm. Break into bite-size pieces