Start by preheating your oven to 425°F. Bring a large pot of salted water to a boil and cook the quartered potatoes until they are just tender, around 10 minutes. Drain the potatoes thoroughly.
In a large mixing bowl, combine the cooked potatoes, shrimp, corn, sausage, sliced lemons, garlic powder, Old Bay seasoning, melted butter, and olive oil. Season generously with kosher salt and freshly ground black pepper, and toss everything until well mixed.
Spread the mixture evenly across two large baking sheets, ensuring the ingredients are in a single layer. Bake in the preheated oven for 13 to 15 minutes, or until the shrimp are fully cooked and the corn is tender.
While the sheet pan is baking, prepare the Old Bay Mayo. In a small bowl, whisk together the mayonnaise, chopped chives, Old Bay seasoning, Dijon mustard, and the lemon juice and zest.
Once the shrimp boil is ready, garnish with freshly chopped parsley and serve immediately with the prepared Old Bay Mayo on the side. Enjoy your flavorful shrimp boil!