Heat the oil in a large skillet over medium heat. Saute the ham and onion in the skillet for 5 minutes. Add 1/2 the amount of juice from the can of pineapple and allow it to be absorbed by the ham, about 1 to 2 minutes.
Stir in the pineapple chunks, apple and brown sugar. Pour in any remaining pineapple juice only if mixture is getting too thick. Stir all ingredients together well and allow to heat through, about 5 minutes. Season with salt and pepper to taste.