Preheat oven to 375 degrees F. In medium saucepan over medium high heat, combine peach preserves, lemon juice, and ground ginger. Cook 3 minutes, or until preserves are melted, stirring constantly. Add pear slices; simmer 5 minutes more.
Meanwhile, in small bowl, combine flour, oats, brown sugar, cinnamon, and salt. With pastry blender or fork, blend in margarine until mixture resembles cornmeal. Add milk; toss to combine.
Pour pear mixture into four 10-inch custard cups. Sprinkle oatmeal topping evenly over surface of pear mixture. Bake crumble 25 to 30 minutes, or until top is lightly browned and bubbling.