Pre-heat oven to 350 F.
Combine flour, oats, baking soda, cinnamon, salt. Set aside.
Cream margarine and gradually add brown sugar and white sugar.
Beat until light and fluffy.
Add egg and vanilla to margarine mixture and mix well.
Alternate adding dry ingredients and pumpkin to the margarine mixture. Mix well after each addition.
Stir in chocolate chips. For small cookies, place spoonfuls of batter on a lightly greased cookie sheet.
For large cookies, use two or three spoonfuls of batter and spread into a pumpkin shape.Bake for 20 to 25 minutes.
To decorate: Make your favourite buttercream icing. Divide the icing and add different flavours and colours. Spread icing over cookies and decorate with candies.