Coat 2 (4-inch) tartlet pans with cooking spray. Combine graham cracker crumbs, 2 teaspoons sugar, and margarine; press evenly onto bottoms and up sides of tartlet pans.
Combine powdered sugar and next 5 ingredients in a small bowl; beat at medium speed of an electric mixer until smooth. Pour mixture evenly into prepared crusts. Bake at 350° for 20 minutes or until set. Turn off oven, and leave cheesecakes in oven 30 minutes. Remove from oven; let cool to room temperature on a wire rack. Cover and chill at least 3 hours. Garnish with orange slices, if desired.