Preheat the oven to 375F and grease a 9 x 9-inch square baking dish.
Dice the pears on a cutting board and set aside.
Make the mixture:
In a medium mixing bowl, combine oats, baking powder, salt, cinnamon, and brown sugar.
In a large bowl, whisk the milk and the egg. Then, add the melted butter, and vanilla extract. Add the oat mixture into the large bowl and mix all ingredients to form a thick oat batter. Add the diced pears to the large bowl and fold with a spatula to combine.
Pour the oatmeal and pear mixture into the prepared baking dish. If necessary, spread the pears around to ensure they're distributed around the dish.
Bake:
Bake for 35 minutes in the preheated oven until the top is golden and the oat mixture is set. Remove from oven and allow the mixture to cool slightly before serving.
Notes
Swap the 4 medium pears for 2 cans of pears, without the juice.