Step 1) Preheat oven to 375°F. Lightly spray 2 baking sheets with cooking spray. Set aside.
Step 2) Stir together flour, sugar, baking powder and salt in a large bowl.
Step 3) Cut cold butter into flour mixture with a pastry blender or two knives until mixture resembles coarse meal. Stir in strawberries, blueberries, and lemon zest.
Step 4) Make a well in the center of mixture and add buttermilk, egg, oil and vanilla, stirring until just combined. Do not overmix.
Step 5) Divide the dough in half. Dough will be sticky. Place each half on a baking sheet (dough will spread when baked) and pat into a 6-inch disk with floured hands.
Step 6) Bake for 15 to 20 minutes, or until edges are golden brown. Let cool for at least 5 minutes. Separate each disk into 8 wedges using a knife or pizza cutter. Transfer to a platter.
Step 7) Whisk together glaze ingredients until smooth in a large bowl. Drizzle glaze over the scones.