Grouper is a dense whitefish, not oily like mackerel. So you can do anything with it that you'd do with say, cod, or snapper.
It's great in Oriental dishes like steamed w/black bean sauce, or cut in thin slices and made into tempura.
My Hawaiian Aikido sensei makes a baked version -
SENSEI'S BAKED FISH
Fish steaks like grouper or mahi-mahi
Panko bread crumbs
Lemons or limes
Preheat oven to 350. Salt and pepper fish and place in a buttered baking dish. Spread a layer of mayonnaise over the top of the fish; then sprinkle bread crumbs over top; squeeze juice of lemon or lime over and drizzle with melted butter. Bake til fish is flakey and done.
Because it's a mild fish, it will take well to just any type of seasoning you want to use on it - Italian, Mexican, Oriental, etc. It's one of our 'local' fishes here in Charleston, and all the restaurants have some version of it on their menus.
One of my favorite ways to do grouper masteraznchefjr is to either grill it with salt, pepper, and lime or broil - then when almost done (just minutes to go) top with homemade pesto and some fresh-grated Parmesan cheese - stick under broiler until cheese melts somewhat. I also make my pesto with fresh limejuice.