In a large bowl, add butter and melt in the microwave. Then add brown sugar and eggs and mix well.
Add baking powder, vanilla extract, cinnamon and salt and mix well.
Stir in milk and oats until well combined. Fold in diced apples. Pour batter into prepared pan(s).
To Bake: Preheat oven to 350 degrees and bake for 35-45 minutes or until center is set. Eat warm with milk poured over the individual serving.
To Freeze: Pour batter into prepared pan and cover with plastic wrap and then foil. Or pour batter into smaller foil pans, cover in plastic wrap and then place entire pan in freezer bag.Thaw overnight in the refrigerator before baking in the morning following above directions.