Preheat the oven to 180 C / Gas 4. Butter a 12-cup muffin tin or line with paper cases.
Sieve the flour, baking powder, caster sugar and salt together into a large bowl.
Whisk the eggs in a medium bowl with the olive oil and milk. Pour into the flour mixture and stir just until dry ingredients are moistened.
Quickly stir in the berries. Fill muffin cups 2/3 full.
Bake in the preheated oven until a skewer inserted near the centre comes out clean, about 20 minutes. Let cool for 5 minutes before turning out of the muffin tin. Serve warm, or cool completely on a wire rack.