Preheat an outdoor grill over high heat. Cut 4 sheets of heavy duty foil 12-inches long.
Divide shrimp, sausage, corn, potatoes, and garlic, evenly over the foil sheets. Drizzle with olive oil. Sprinkle with Old Bay seasoning and salt and pepper to taste. Toss gently to combine. Top each packet with parsley, lemon and a tablespoon of butter.
Fold the foil packets crosswise over the shrimp boil mixture to completely cover the food. Roll the top and bottom edges to seal them closed.
Place foil packets on the grill and cook until just cooked through, about 20-25 minutes.