Add cranberries to a food processor and pulse to finely chop the berries.
Add sugar to the cranberries and pulse until mixed. Transfer cranberries to a bowl.
Cover the bowl with plastic wrap and refrigerate overnight (or at least 2 hours).
Add the crushed pineapple, grapes, and pecans to the cranberries and mix it all together.
Add the mini marshmallows and mix. Add the Cool Whip and fold everything together until thoroughly mixed.
Serve immediately or cover and store in the refrigerator. I like to top this salad with some cranberries, grapes, pecans, and marshmallows for garnish. If you're going to do this, set a little of each aside before starting the recipe.
If you prefer (or if there's a sale), you can use red seedless grapes or a combination of red and green grapes.