Heat oven to 350°F. Spray 3 baking sheets with cooking spray; set aside. Stir egg whites, coconut, oats, vanilla, sugar and salt in a bowl until well blended. Drop tablespoons of dough onto baking sheets, half an inch apart. Bake macaroons until light golden, 12 to 15 minutes. Transfer to a wire rack and cool completely. Place chocolate morsels and margarine in a glass bowl or measuring cup. Microwave on high until chocolate melts completely, 40 to 50 seconds, or melt in a 350° oven 5 to 6 minutes. (Do not overheat chocolate or it will scorch.) Dip a metal teaspoon into warmed chocolate and gently drizzle chocolate over cookies in a zigzag pattern. Cool completely. Store in an airtight container in a cool, dry place for up to 3 days.