Heat oven to 350 degrees.
Beat together margarine and sugars until creamy.
Add pumpkin, egg, and vanilla; beat well.
Combine oats, flour, pumpkin pie spice, baking soda and salt; add to above mixture and mix well.
Drop by rounded tablespoonfuls onto ungreased cookie sheet.
Bake 11 to 13 minutes until golden brown.
Cool 1 minute on cookie sheet; remove to wire rack. Cool completely.
For frosting, beat together cream cheese, milk, and vanilla until smooth. Gradually beat in powdered sugar until smooth; tint with food coloring, if desired. Frost top of each cookie. Store in tightly covered container in refrigerator.