Preheat the oven to 400 degrees F. Lightly coat a heavy baking sheet with cooking spray.
In a medium bowl, sift together the flour, brown sugar, baking powder, salt, and nutmeg. Using a pastry blender, or 2 knives, cut in the margarine until the mixture resembles coarse crumbs. Toss with the blueberries.
In a small bowl, whisk together the evaporated milk, egg, and vanilla extract. Make a well in the center of the flour mixture. Pour in the egg mixture, stirring just until the dry ingredients are moistened. Do not overmix.
Drop by heaping spoonfuls on the prepared baking sheet, making 6 mounds. Bake for 12 to 15 minutes, until golden. Cool on a rack for a few minutes before serving hot or warm.