Melt 1 cup margarine in large saucepan; remove from heat. Add brown sugar and eggs; blend well. Lightly spoon flour into measuring cup; level off. Add flour, coconut, pecans, salt and vanilla; mix well. Spread half of batter in greased pan. Drop chocolate mixture by tablespoonfuls over batter; carefully spread to cover. Drop remaining batter by teaspoonfuls over chocolate mixture; swirl slightly with tip of knife to marble mixture.