Start by preheating your oven to 400 degrees F. Prepare a baking sheet with a light coating of oil or nonstick spray.
Boil the potatoes in a large pot of salted water until they are nearly tender, which should take about 10-13 minutes. Add the corn during the last 5 minutes of boiling. Once done, drain everything well.
Mix together the melted butter, minced garlic, and Old Bay seasoning in a small bowl.
Spread the potatoes, corn, shrimp, and sausage evenly on the prepared baking sheet. Drizzle the butter mixture over the top and gently toss everything to ensure it’s well-coated.
Bake in the oven for 12-15 minutes, until the shrimp turn opaque and the corn is tender.
Serve hot with lemon wedges and a sprinkle of parsley if desired.