Preheat the grill to medium high.

Cut the pineapple into 1-inch rings.

Grill the pineapple until grill marks appear, about 3 minutes per-side.

Reserve two rings for garnish. Cut the remaining rings, removing the skin and core. Add the pineapple flesh, about 2 cups, to a blender or food processor along with the lemon, brown sugar and whiskey. Blend until smooth. Add to a serving container, refrigerate until chilled, can be made a day ahead of time.

Just prior to serving stir in the triple sec, beer and peaches.