Heat oven to 350°F. In large bowl, break up cookie dough. Stir or knead in flour until well blended. Work with half the dough at a time; refrigerate remaining dough until needed.
Shape dough into 70 (3/4-inch) balls; reserve 7 balls. Roll each of the remaining balls in green sugar. To form each shamrock, place 2 balls with sides touching and 1 ball on top on ungreased cookie sheets. For stems, divide each reserved ball into 3 pieces. Roll each piece into ball, then in green sugar; shape into a triangle. Place 1 triangle pointed side up at bottom of each cookie between 2 balls for stem.
Bake 10 to 12 minutes or until set. Cool 1 minute; remove from cookie sheets to cooling rack. Cool completely, about 15 minutes.