Heat oven to 350'F. Beat margarine and sugar in large bowl until fluffy. Blend in egg and vanilla. Add combined oats and flour; mix well. Shape into 1" balls; roll in chopped nuts. Place 2" apart on ungreased cookie sheet. Make indentation in center of each ball with thumb. Fill each thumbprint with about 1/4 teaspoon jelly. Bake 12-15 minutes or until light golden brown. Cool completely on wire rack. Store loosely covered.