Add the herbs, lemon and capers to the cooked quinoa, mix well. Add a drizzle of olive oil to help to combine, season to taste.
Place the mackerel skin side down on a lightly greased and lined tray.
Gently press the quinoa topping onto the mackerel.
Bake at 180°C, Gas mark 4, for 20 minutes, until lightly browned.