Whisk the oil, orange juice, zest and eggs lightly in a bowl. Add the flour, baking powder and sugar and stir until just combined. Fold in two-thirds of the blueberries.
Spoon the mixture into your muffin tray, two-thirds full.
Scatter over the remaining blueberries and a little extra sugar and bake for 30 minutes or until a skewer comes out clean.