In a small pot, combine butter, onion, garlic. Simmer on low heat on a stove top. Add salt and pepper to taste.
Prep Oysters by thoroughly cleaning shell with a brush under running water. Discard any oysters that are open as these oysters are dead and inedible. Pry open oysters with an oyster shucker and remove top shell. Place the remaining half in the Outset Grill Pan and coat with butter sauce.
Preheat grill to medium high heat. Place grill pan on high heat and close lid. Allow oysters to cook for 6-8 minutes with the grill vents open.
Remove from heat and allow pan to cool. Serve with a dash of lemon juice or hot sauce. This pan also doubles as the perfect pan for serving!