Light your charcoal and allow it to heat until the coals are glowing red with a light layer of white ash.
Shuck the oysters. Keep as much of their natural liquor in the shell as possible. Arrange them on a tray so they’re stable and ready for the grill.
In a medium bowl, combine the Parmigiano Reggiano, Pecorino Romano, chopped parsley, a squeeze of fresh lemon juice, salt, and pepper.
Toss gently with a fork to keep the cheese light and fluffy. Set aside.
In a small saucepan or heatproof container, melt the butter over low heat. Stir in fresh thyme, rosemary, and minced garlic. Set aside.
Place the oysters directly on the grates. Make sure your oysters are close together and touching.
Sprinkle each oyster generously with the cheese mixture.
Ladle the melted butter over the oysters. Be fast, you do not want your oysters to pop or cook too long.
Sprinkle more of the cheese mixture over the top to your preference. The oysters are done when the cheese is melted, lightly golden, and the edges of the oysters start to curl. 2-3 minutes.
Remove the oysters with tongs, transfer them to a platter, and serve with toasted bread.