Clean, wash and drain the chicory and radicchio. Cut lettuce leaves into bite-sized pieces. Peel onion, cut into fine slices and halve as desired. Peel oranges so that the white skin is completely removed.
Cut out the fillets from the parting skins. Squeeze the remaining juice out of the orange. Cut avocados in half, remove stones. Cut out balls from the flesh and sprinkle with lemon juice. Coarsely chop the walnuts.
Mix vinegar with orange juice. Season to taste with sugar, salt and pepper. Whip the oil into it. Mix all salad ingredients with the vinaigrette. Serve garnished with a slice of orange if you like.
It goes well with farmhouse bread.