If fish fillets are large, cut into serving pieces.
Mix margarine and lemon juice.
In another bowl, mix flour, salt and white pepper.
Dip fish into margarine mixture; coat fish with flour mixture.
Place fish in ungreased square baking dish, 8x8x2 inches.
Pour remaining margarine mixture over fish; sprinkle with paprika.
Cook uncovered in 350° oven until fish flakes easily with fork, 25 to 30 minutes.
Garnish with parsley sprigs and lemon slices if desired.