Slice pineapples into chunks or rings. If desired, save one half of pineapple shell for serving.
Mix brown sugar and rum. Pour over pineapple pieces in a large bowl or plastic bag.
Cover bowl with plastic wrap. If you are using a plastic bag, I suggest placing it into a bowl to catch leaks.
Place bowl into refrigerator. Marinate two to four hours.
Prepare the grill or broiler for high heat. Grill for 10 minutes until brown and crispy, flipping occasionally.
Remove to serving dish or reserved half pineapple shell.
This recipe was adapted from Dr. BBQ's Big-Time Barbecue Cookbook.