Wash salads and spin dry well. Fillet the grapefruit, collecting the juice separately. Cut the grapefruit fillets into bite-sized pieces.
Mix the yogurt, white wine vinegar, olive oil, mustard, honey, orange peel, salt, pepper and salad herbs until smooth. Season to taste with the collected grapefruit juice.
Mix the lettuce with the yoghurt dressing well, then carefully fold in the grapefruit pieces.