Preheat the oven to 400°F (200°C) and line a 12-cup muffin tin with paper liners or coat with cooking spray.

In a large mixing bowl, whisk together wheat bran cereal, all-purpose flour, granulated sugar, baking powder, baking soda, salt, ground cinnamon, and ground nutmeg until evenly combined.

In a medium mixing bowl, whisk the eggs, whole milk, melted butter, and vanilla extract until smooth and slightly frothy.

Pour the wet mixture into the dry ingredients and stir gently with a spatula just until no dry streaks remain; the batter should still be slightly lumpy.

Fold in the raisins or dried cranberries with a few gentle strokes to distribute evenly.

Scoop the batter into the prepared muffin cups, filling each about three-quarters full for even rising.

Bake for 18–22 minutes, or until the tops are golden brown and a toothpick inserted in the center comes out clean or with a few moist crumbs.

Cool the muffins in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving or storing.