Preheat oven to 350 degrees F. Spray an 8.5 x 4.5 loaf pan with nonstick cooking spray and set aside. In a large bowl add the buttermilk and egg. Whisk together.
Add the Bisquick to the bowl and mix together with a rubber spatula.
Add the zucchini, sharp cheddar cheese and scallions to the bowl and mix together, do not overmix.
Pour the batter into the loaf pan. Bake 45-55 minutes, or until a toothpick inserted in the middle comes out clean.