Coarsely chop frozen blackberries, and place them back in the freezer until ready to stir into the batter. To freeze muffins, let cool completely, and place in zip-top plastic bags. Reheat in microwave 20 seconds.
Yield: 17 muffins (serving size: 1 muffin)
2 cups all-purpose flour (about 9 ounces)
1 cup rolled oats
1 cup packed dark brown sugar
1 1/2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1/2 teaspoon apple-pie spice
1 cup fat-free milk
3 tablespoons butter, melted
1 teaspoon vanilla extract
1 large egg, lightly beaten
1 1/2 cups frozen blackberries, coarsely chopped
Cooking spray
1/4 cup granulated sugar
Preheat oven to 400°.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 6 ingredients (through apple-pie spice) in a large bowl. Make a well in center of mixture. Combine milk, butter, vanilla, and egg in a small bowl; add to flour mixture, stirring until just moist. Gently stir in blackberries.
Spoon 1/4 cup batter into each of 17 paper-lined muffin cups coated with cooking spray. Bake at 400° for 16 minutes. Sprinkle muffins evenly with granulated sugar; bake 3 minutes or until muffins spring back when touched lightly in center. Cool in pans 10 minutes on wire racks.