Preheat the oven to 350°F. Grease an 8×11-inch baking dish.
Add the pears to a large bowl.
6 cups peeled, cored, and sliced pears
Add the brown sugar, flour, lemon juice, cinnamon, nutmeg, vanilla, and salt. Toss until the pears are evenly coated.
¼ cup packed light brown sugar, 2 tablespoons all-purpose flour, 1 tablespoon fresh lemon juice, 1 teaspoon ground cinnamon, ¼ teaspoon ground nutmeg, ½ teaspoon vanilla extract, Pinch of salt
Spread the pear mixture evenly in the prepared baking dish.
In a separate medium bowl, stir together the oats, flour, and brown sugar. Cut in the cold butter until the mixture forms crumbs with some larger clumps. Sprinkle the topping evenly over the pears.
1½ cups old-fashioned oats, 1 cup all-purpose flour, 1 cup light brown sugar, ½ cup cold salted butter
Bake for about 40–50 minutes, or until the topping is golden brown and the pear filling is bubbling around the edges. If the topping browns too quickly, loosely tent it with foil toward the end.
Let it stand for 10–15 minutes before serving.
Notes
Pears: Baking pears, like Bosc and Anjou, work best. Slightly underripe Bartlett pears can also be used. I don't recommend ripe or overripe Bartlett pears as they will get mushy when baked.
Spices: You can adjust the spices according to your tastes.
Oats: Old-fashioned oats or rolled oats work best.
Brown sugar: Light brown sugar or dark brown sugar will work. Feel free to use more or less of the sugar in the filling depending on how sweet your pears are.
Butter: I use salted butter. If you’re using unsalted butter, add 1/4 teaspoon salt along with the butter.