Place bananas in the bowl of a stand mixer fitted with the paddle attachment. Beat on low speed for 1 minute until bananas are mashed.

Add ¼ cup all-purpose flour, whole wheat flour, oats, ¼ cup sugar, milk, oil, yeast, salt, and 1 teaspoon cinnamon. Beat on medium speed for 3 minutes.

Switch to the dough hook and gradually add remaining all-purpose flour until a soft dough forms. Knead on low speed for 5 minutes, until smooth and elastic.

Shape dough into a ball and place in a greased bowl, turning once to coat. Cover and let rise in a warm place for 1 hour or until doubled in size.

Grease a 12-cup bundt pan with 1 tablespoon melted butter.

In a small bowl, combine remaining ½ cup sugar and 1 teaspoon cinnamon.

Turn dough onto a lightly floured surface, pat into a 9-inch square, cut into 1-inch pieces, and roll into balls.

Dip dough balls into remaining melted butter, then roll in cinnamon sugar. Layer evenly in prepared bundt pan.

Cover and let rise for 1 hour until puffy. Preheat oven to 350°F.

Bake for 30 minutes or until golden brown and set.

Immediately invert onto a serving plate. Cool slightly before serving.