Clean and oil grill grates. Preheat grill to 350-400 °F.
Cut the rind off of pineapple and core out. Slice into 1/2'' slices. Cut them in half or slice them into spears, according to your preference.
Place pineapple in resealable gallon bag or container. Sprinkle brown sugar over the top. Mix until completely coated. Let rest 10 minutes.
Place pineapple on grill and brush remaining brown sugar that's left in bag or container over the top. Grill each side 2-3 minutes.