Preheat the oven to 375°F. Prepare a 12-cup muffin tin with non-stick spray or line with paper cups. Set aside.
In a medium mixing bowl, mash 2 ripe bananas with a fork. Stir in ¾ cup granulated sugar, ½ cup cooking oil, ½ cup milk, 1 large egg (beaten), and 1 teaspoon vanilla until combined.
Add 2 cups all-purpose flour, 1 teaspoon baking soda, ½ teaspoon ground cinnamon, and ½ teaspoon salt, to the batter. Stir until just combined and there are no visible streaks of dry flour.
Evenly portion the batter into the muffin cups. Top each evenly with ¼ cup walnuts on each top if desired. Bake for 18-22 minutes or until a toothpick inserted in the center of a muffin comes out clean or the tops spring back when lightly pressed.
Notes
Storing Muffins: Banana bread muffins can last up to four days at room temperature if stored in an airtight container. They can also be frozen for up to three months.