In a small bowl, cream butter and brown sugar. Beat in egg and vanilla. Combine the flour, oats, baking powder, baking soda and salt; add to creamed mixture and mix well. Stir in 1 cup M&M's.
Press onto a greased 12-in. pizza pan. Sprinkle with nuts, coconut and remaining M&M's; press lightly into dough. Bake at 350° for 18-22 minutes or until golden brown. Cool on a wire rack. Cut into wedges.