Preheat oven to 400°.
Combine first 6 ingredients in a medium bowl; stir well. Add pear and walnuts; toss gently to coat. Make a well in center of mixture. Combine milk, oil, and egg; and stir well. Add to flour mixture, stirring just until moist (dough will be sticky).
Divide batter evenly among 12 muffin cups coated with cooking spray; sprinkle with granulated sugar. Bake at 400° for 20 minutes or until a wooden pick inserted in center comes out clean. Remove muffins from pans immediately; let cool on a wire rack.