PREHEAT oven to 400°F. Mix 3/4 cup of the flour, the cereal, 1/3 cup of the brown sugar, 3/4 tsp. of the cinnamon and the nutmeg in large bowl. Using pastry blender or 2 knives, cut in 6 Tbsp. of the butter until mixture resembles coarse crumbs. Set aside.
MIX remaining 3 cups flour, remaining 1 cup brown sugar, remaining 1 tsp. cinnamon and the baking powder in large bowl; set aside. Melt remaining 8 Tbsp. butter. Place in small bowl. Add milk and egg product; beat with wire whisk until well blended. Add to flour mixture; stir just until moistened. (Batter will be lumpy.) Add blueberries and walnuts; stir just until evenly distributed. Spoon evenly into 20 greased medium muffin cups, filling each cup 2/3 full. Sprinkle with the crumb mixture.
BAKE 20 to 24 min. or until toothpick inserted in centers comes out clean. Cool 10 min.; remove to wire racks to cool completely.