MIX flour, sugar, baking powder, cinnamon, nutmeg and salt in large bowl. Beat eggs, milk and oil in small bowl with wire whisk until well blended. Add to flour mixture; stir just until moistened. (Batter will be lumpy.) Stir in cereal, apple and walnuts.
SPOON batter into greased or paper-lined muffin pan, filling each cup 2/3 full.
BAKE at 425°F for 20 minutes or until toothpick inserted in centers comes out clean. Let stand 5 minutes. Serve warm.