Preheat Oven To 325 Degrees F (165 Degrees C). Lightly Butter A 9X13-Inch Glass Baking Dish And Set Aside. Season The Grouper Fillets With Salt, Lemon Pepper, Garlic Powder, And Onion Powder; Place Into Prepared Baking Dish. Spread About 2 Tablespoons Of Softened Butter Over The Top Of Each Fillet. Pour In The Lime And Orange Juices, Then Cover Each Fillet With 3 Slices Of Lime, And 2 Slices Of Orange. Bake In Preheated Oven Until Fish Is Opaque And Flakes Easily With A Fork, About 15 Minutes.