Bring a large pot of salted water to a boil. Cook the potatoes until they are just tender and partially cooked, about 10-13 minutes. Add the corn in the last 5 minutes of cooking. Drain well.
In a small bowl, mix together the melted butter, minced garlic, and Old Bay seasoning.
Spread the potatoes, corn, shrimp, and sausage in a single layer on a greased baking sheet. Gently toss with the butter mixture until well coated.
Bake in the oven for 12-15 minutes, or until the shrimp turn opaque and the corn is tender.
Serve immediately, garnished with lemon wedges and a sprinkle of fresh parsley.