Preheat oven to 350° and grease a 10-inch cast iron skillet or 8x8 baking pan.
In a large bowl, combine the pears, 2 tbsp brown sugar, cornstarch, cinnamon, and vanilla. Toss until the pears are well-coated, then pour in the prepared skillet or pan.
In a medium bowl, stir together the rolled oats, brown sugar, flour, cinnamon, and salt until well-combined. Add the cubed butter, working it in with a pastry cutter or fork until crumbly and well-combined. Stir in the chopped pecans.
Top the pears with the cinnamon pecan topping evenly.
Bake in the preheated oven for 45-50 minutes, or until the pears are soft and the topping is crisp and golden. Allow to cool at room temperature for about 30 minutes, then serve with ice cream!