Preparation: Preheat your oven to 400°F (200°C). Lay out a large piece of heavy-duty aluminum foil on a baking sheet.
The Seasoning Toss: In a large mixing bowl, combine the shrimp, sliced sausage, corn medallions, and cherry tomatoes. Pour over the melted butter, minced garlic, Old Bay seasoning, and lemon juice. Toss until everything is generously and evenly coated.
Create the Packet: Pour the mixture into the center of the foil. Bring the long edges of the foil together and fold them down tightly. Fold the ends inward to create a fully sealed packet that will trap the steam.
The Bake: Place the baking sheet in the oven and roast for 15–20 minutes.
Optional Char: For a bit of extra color, carefully open the foil packet (watch out for hot steam!) and place it under the broiler for 2–3 minutes until the sausage edges are slightly crisp and caramelized.
Serve: Sprinkle with a shower of fresh parsley. Serve directly from the foil for a rustic, coastal feel, making sure to provide plenty of bread to soak up the garlic butter juices at the bottom!