To save time, use a food processor to slice the potatoes.
Preheat oven to 400 degrees F. Coat a 9-by-13-inch baking dish with cooking spray.
Toss potatoes with garlic, oil, 1/4 teaspoon salt and a generous grinding of pepper in the prepared pan. Cover with foil and roast until tender when pierced with a knife, 30 to 40 minutes.
Place fish fillets on potatoes, skin-side down; sprinkle with remaining salt, pepper, lemon juice and parsley. Bake until the fish is opaque in the center, 10 to 15 minutes. Serve with lemon wedges.
1 1/2 starch, 3 lean meat, 1 1/2 fat