Squeeze two of the oranges and reserve juice. Take the other two, cut into supremes, and reserve. In a small heavy saucepan, cook the butter over medium heat until it foams, the foam then subsides, and the butter begins to brown and smell toasty. Add the reserved orange juice, the lemon juice, wine, sugar, and half the salt and pepper. Boil the mixture until well reduced, 15 to 20 minutes. Stir in the orange sections and olives and reserve in a warm place.
Heat grill to high. With a very sharp knife, score the skin side of each snapper fillet. The cut should pierce the skin but not the flesh. Brush or rub the fish with the olive oil and season evenly with remaining salt and pepper. Brush the grill well, wipe with an oiled paper towel, and place the fish fillets on the grill skin side down. Grill 34 minutes on the skin side, until skin is crispy and a 1/2-inch margin of opaque flesh has formed all around the edges of the fillet. Flip fish and cook one minute on flesh side. Remove from grill and place on plates, skin side up. Stir parsley into warm sauce and taste for seasoning. Spoon sauce over fish fillets and serve.
c.1997, M.S. Milliken & S. Feniger, all rights reserved