Melt the butter and blend it with the other crust ingredients until it almost but not quite sticks together. Divide this into four portions, and cover the top of each grouper fillet with a layer of the crust.
Place the encrusted fish fillets in a large skillet or baking pan, lightly oiled with olive oil. Sprinkle lemon juice over all. Bake the fish in a preheated 400- degree oven for 10-12 minutes. (To test the fish for doneness, push a kitchen fork into the center of the biggest fillet. Hold it there for five seconds, then pull it out. Touch the tines of the fork carefully to your lips. If it feels even warm, the fish is done.)