PREHEAT oven to 350°F. Combine graham crumbs, flour, baking powder, baking soda, cinnamon and nutmeg; set aside.
BEAT eggs in large bowl with electric mixer on high speed 2 minutes or until thickened. Add oil, brown sugar and vanilla; beat until well blended. Stir in the graham crumb mixture, carrots and walnuts. Pour into greased and floured 12-cup fluted tube pan.
BAKE 1 hour to 1 hour 10 minutes or until toothpick inserted near center comes out clean. Cool in pan 10 minutes. Remove from pan; cool completely on wire rack. Sprinkle with powdered sugar just before serving.