Pre-heat oven to 375 degrees and line three muffin tins with papers (you'll only need 6 papers in the third tin). If you only have one tin, you can bake these in two batches.
In a medium bowl, whisk together 2 cups oats, flour, baking powder, baking soda, salt, oat bran, and cinnamon.
In the bowl of a stand mixer or in a large bowl with a hand mixer, beat together butter, granulated sugar, and brown sugar at medium-high speed until light and fluffy, 2-3 minutes.
Mix in eggs one at a time, followed by vanilla. Reduce mixer speed to low and slowly add in flour mixture until it’s just combined, taking care not to over-mix.
Gently mix in the sour cream and fold in the raisins.
Put about 2 ¾ cups of the batter into a separate bowl and stir in the rest of the oats and the coconut. This batter is going to be used for the muffin tops.
Spoon about 2 ½ Tbsp of the plain (coconut-free) batter into the bottom of muffin papers. Top with about 1 ½ Tbsp of the topping batter with extra oats and coconut.
Bake muffins for about 18-20 minutes until the tops are turning golden and a toothpick inserted into the center comes out clean. Let cool in tins for a couple minutes before moving to wire racks to cool completely.