In a large bowl beat egg with a whisk; stir in milk, oil, bran cereal, dried cranberries, and brown sugar. Let stand for 5 minutes. In another large bowl combine flour, baking powder, baking soda, and salt; stir bran mixture into flour mixture just until moistened (batter should be lumpy).
For each muffin, layer 2 foil bake cups together (remove paper liners from foil cups and save for another use). Spoon batter into cups, filling each two-thirds full. If desired, sprinkle with coarse sugar.
Prepare grill for indirect grilling, except omit drip pan. Test for medium heat above the center of grill. Using a wide metal spatula, carefully place muffin cups, one at a time, on the grill rack in the center of the grill (not over heat). Cover and grill for 15 to 20 minutes or until a toothpick inserted in center of muffin comes out clean. Serve muffins warm. Makes 12 muffins.