Preheat the oven to 350°F, and coat 13 muffin cups with nonstick cooking spray. (If using liners, then line 13 muffins cups with liners and coat them with cooking spray.)

In a medium bowl, stir together the oats, Greek yogurt, ¼ cup of milk, and vanilla extract. In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Whisk in the orange zest. In a third bowl, whisk together the butter, egg whites, and liquid stevia. Stir in the orange juice. Stir in the oat mixture, mixing until no large lumps remain. Alternate between adding the flour mixture and remaining ½ cup of milk, beginning and ending with the flour mixture, and stirring just until incorporated. (For best results, add the flour mixture in 3 equal parts.) Gently fold in the cranberries.

Divide the batter between the prepared muffin cups. Bake at 350°F for 23-26 minutes or until the top feels firm to the touch and a toothpick inserted into the center comes out clean. Cool in the pan for 5 minutes before transferring to a wire rack to cool completely.