Cut the top and bottom off the pineapple and discard them. Using a pineapple corer, place it on the top of your pineapple and twist it through all the way to the bottom. Slowly pull it out to remove the flesh from the skin and remove the core.
Make a slice down one side of the pineapple so the pineapple separates into round slices.
Spray or brush your grill or griddle with cooking oil and turn on medium-high heat.
Once the grill is hot, using tongs or a spatula, place pineapple rings on the grill or griddle. Grill the pineapple slices for about 3 to 5 minutes per side or until you reach the desired doneness. Timing is personal preference and you really can't go wrong unless they burn, so just keep an eye on the slices and the clock.
Using tongs or a spatula, remove the slices from the grill. Transfer to a platter and serve immediately.