Heat oven to 325°F. Beat margarine and sugar until creamy. Add egg and vanilla; beat well. Add combined flour, oats and salt; mix well.
Shape dough into 1-inch balls. Press desired candy piece into center of each ball; shape dough around candy so it is completely hidden. Roll cookies in colored sugar or candy sprinkles until evenly coated. Place 1-1/2 inches apart on ungreased cookie sheets.
Bake 14 to 17 minutes or until set and bottoms are light golden brown. Remove to wire rack. Cool completely. Store tightly covered.
For powdered sugar coated cookies, bake uncoated cookies as directed above. Remove to wire rack; cool 5 minutes. Place about 3/4 cup powdered sugar in plastic bag. Gently shake 3 to 4 cookies in powdered sugar until coated. Repeat with remaining cookies. Sift remaining powdered sugar over cookies. Cool completely.