Combine buttermilk, rolled oats, and raisins in a bowl. Cover and refrigerate 8 hours to overnight.

Preheat the oven to 400 degrees F (200 degrees C). Liberally grease a 12-cup muffin tin.

Remove buttermilk mixture from the refrigerator. Mix flour, baking powder, baking soda, salt, and wheat germ together in a bowl.

Beat butter and brown sugar together in a large mixing bowl until light. Add honey and egg and mix well.

Add flour mixture and buttermilk mixture in alternating batches to the mixing bowl with the butter mixture; stir until batter is evenly moistened.

Divide batter evenly into the prepared muffin tin.

Bake in the preheated oven until set and golden brown, 22 to 28 minutes.