Preheat oven to 300 degree F. Place cheese crackers and wheat crackers in a large roasting pan. Bake about 5 minutes or until warm.
Add pretzel twists and nuts to crackers. Pour melted butter or margarine over mixture. Sprinkle with salad dressing mix; stir well to coat. Bake for 20 minutes more, stirring once. Spread mixture on foil to cool. Store in an airtight container for up to 1 week.