PREHEAT oven to 350°F. Mix flour, wafer crumbs, baking powder and salt; set aside.
BEAT margarine and sugar in medium bowl with electric mixer on medium speed until creamy. Add eggs; beat until light and fluffy. Blend in bananas. Add flour mixture alternately with milk, beating well after each addition. Stir in 1/2 cup of the walnuts. Spread into greased 9x5-inch loaf pan. Sprinkle with remaining 1/4 cup walnuts.
BAKE 1 hour 10 min. or until toothpick inserted in center comes out clean. Cool 10 min. Remove from pan to wire rack; cool completely. Cut into 16 slices to serve.