Preheat oven to 350°.
Combine first 5 ingredients in a large bowl; toss gently to coat. Spoon pear mixture into an 8-inch square baking dish coated with cooking spray.
Combine 1/2 cup all-purpose flour and next 4 ingredients (1/2 cup all-purpose flour through salt) in a medium bowl, and cut in 2 tablespoons chilled margarine with a pastry blender or 2 knives until mixture resembles coarse meal. Add milk, and toss with a fork until flour mixture is moist.
Drop dough by heaping tablespoons onto pear mixture. Brush melted margarine over dough, and sprinkle with brown sugar. Bake at 350° for 45 minutes or until lightly browned and bubbly.