Melt margarine in large skillet over medium-high heat. Add flour, sugar and coconut to skillet; mix well. Cook 3 to 4 minutes or until mixture is golden brown and crumbly, stirring constantly.
Reserve 1/4 cup crumb mixture for topping. With back of spoon, press remaining mixture firmly in bottom of ungreased 9-inch square pan. Place in freezer for 5 minutes to cool.
In large bowl, combine sherbet and ice cream, swirling to create a marbled look. Spread filling over crust. Sprinkle with reserved crumb mixture. Cover; freeze 4 hours or until firm.
To serve, place in refrigerator for 30 minutes to soften slightly. Garnish individual servings with orange segments.