Heat barbeque or indoor grill to high heat. Toss prawns with olive oil, salt and pepper. Set lettuce into 4 decorative glasses or bowls. Grill prawns 1-2 minutes per side, or until cooked through. Arrange while still warm, or after chilling well, around the rim of the glass or bowl. Spoon cocktail sauce in the centre. Garnish with lemon and parsley.