Adjust an oven rack to the lower-middle position and preheat the oven to 425 degrees F. Line a rimmed baking sheet with aluminum foil.
Make the Topping: In a medium bowl, stir together the oats, flour, sugar, cinnamon, nutmeg and salt. Drizzle the melted butter over the mixture and stir until the mixture resembles wet sand. Set aside.
Make the Filling: In a large bowl, whisk together the sugar, lemon juice, cornstarch and salt. Add the pears and gently stir with a rubber spatula until evenly coated. Transfer the pear mixture to an 8-inch square baking dish.
Sprinkle the topping evenly over the filling. Transfer the dish to the prepared foil-lined baking sheet. Bake until the fruit is bubbling around the edges and the topping is a deep golden brown, about 30 minutes, rotating the sheet halfway through baking. Transfer the baking dish to a wire rack and let cool until warm, about 15 minutes.
Note: The original recipe called for chopped nuts in the crisp topping, but I substituted oats. Feel free to use nuts, if you'd like instead of oats - pecans or walnuts would be great choices!Nutritional values are based on one serving