Marie Callendar's baked goods are all factory produced, so I doubt you will find a recipe. The following is my favorite bran muffin from Maida Heatter's New Book of Great Desserts.
2 oz unsalted butter
1/2 cup dark brown sugar
1/4 cup honey or molasses
2 eggs
1 cup milk
1 1/2 cups All-Bran cereal or wheat bran
5 oz raisins
4 oz (generous cup) walnuts, chopped
1/2 cup whole wheat flour
1/2 cup unbleached white flour
3/4 teasp. Salt
1 1/2 teasp. Baking Soda
Preheat oven to 400 degrees. Line muffin tins with papers, or butter well.
Melt the butter and put in a large bowl. Add the sugar and molasses or honey. Mix well.
In a small bowl beat the eggs. Gradually stir in the milk. Add to the butter mixture, stirring well. Add the raisins and bran, let sit for a few minutes, or refrigerate overnight.
Stir in walnuts and dry ingredients.. Mix only until combines. Put batter in prepared tins, filling 2/3. Bake 15 minutes or just until tops spring back. Remove from tins and cool on wire rack.