Preheat oven to 350�F.
Mix the oats, walnuts, brown sugar, flour, and cinnamon in a medium bowl. Add the oil, and stir until uniform.
Mix the pears, maple syrup, raisins, flour, lemon juice, and ginger in a bowl. Transfer to a 9-by-13-inch baking dish and sprinkle the oat mixture over the pear mixture.
Bake until the pears are tender and the topping is golden, about 45-50 minutes. Let stand for 10 minutes prior to serving.