Heat oven to 350°F. Grease and flour 10-inch tube pan. Lightly spoon flour into measuring cup; level off. In medium bowl, combine flour, coconut, rolled oats, brown sugar and pecans; mix well. With fork or pastry blender, cut in margarine until mixture is crumbly. Set aside.
In large bowl, combine bananas, sour cream and eggs; beat at low speed until smooth. Add cake mix; beat 2 minutes at high speed. Spread 1/3 of batter in greased and floured pan; sprinkle with 1/3 of coconut mixture. Repeat layers 2 more times using remaining batter and coconut mixture, ending with coconut mixture.
Bake at 350°F. for 50 to 60 minutes or until toothpick inserted near center comes out clean. Cool upright in pan 15 minutes. Remove cake from pan; place on serving plate, coconut side up. Cool 1 hour or until completely cooled.