Preheat oven to 350 degrees Fahrenheit. Place sliced pears in the pie crust and toss with lemon juice. Spread out the pears in the pan in an even layer.

In a small mixing bowl, whisk the maple syrup, light brown sugar, cinnamon, nutmeg, ginger, vanilla, salt, and cornstarch until combined. Pour maple syrup mixture over pears and mix until evenly coated.

For the Topping: In a separate medium size bowl, combine and stir the oats, pecans, flour, melted margarine, granulated sugar, cinnamon, nutmeg and salt. Sprinkle topping over the filling.

Bake the pie in the preheated oven for 40 to 45 minutes until the fruit juices are bubbling and the top is golden brown. Fruit should be fork- or knife-tender. Tent with foil if the topping starts to brown too quickly.

Allow the pie to cool slightly before serving. Serve warm or room temperature with vanilla ice cream and/or a drizzle of caramel syrup.