Cook the grains according to pack instructions. Leave to cool, then tip into a bowl and use your hands to mix in the turkey, garlic, coriander, harissa and parsley. Shape into four patties. Cover and chill.
To make the sauce, coarsely grate the courgette, discarding the seeds, then wrap in a clean cloth and squeeze out any liquid. Put in a bowl and mix with the dill, yogurt, 2 tbsp water and the mayonnaise.
Put the peppers on the barbecue and cook for 10-15 mins or until blistered and starting to char. Or, heat a grill to its highest setting and grill for 15-20 mins, turning halfway. Leave to cool a little, then peel and cut into strips.
Toss the rocket with half the oil and lemon juice.
Brush the burgers with the remaining oil and cook for 6 mins each side. Alternatively, heat the oil in a frying pan over a medium heat and fry for 6 mins each side. Serve with the sauce, peppers, beetroot, buns and salad so everyone can assemble their own burger.