Preheat the oven to 390°F and line a muffin tin with paper liners, if desired, placing them in a baking pan if needed.

In a bowl, mix together the flour, granulated sugar, salt, and baking powder. In another bowl, whisk together the oil, milk, and egg.

Add the wet mixture to the flour mixture and stir briefly until just combined. Gently fold in the blueberries.

Divide the batter over the muffin liners and spoon the topping over it. Bake the muffins for 20 to 25 minutes until golden brown and cooked through.

Let the muffins cool briefly in the tin, then transfer them to a wire rack to cool completely. Enjoy!