Preheat oven to 425˚F.
In a large bowl combine the potatoes and corn.
In a separate bowl combine the sausage and shrimp.
Melt the butter, then stir in the olive oil, garlic, old bay seasoning, oregano and Cajun seasoning.
Pour half the seasoning mixture on the potatoes and corn; toss to coat. Pour the remaining mixture on the sausage and shrimp.
Transfer the potatoes to the baking sheet. Bake for 12 minutes. Stir the potatoes and add the corn to the pan. Continue baking for 12 minutes.
Arrange the sausage and shrimp around the potatoes and corn.
Continue to bake for 12 minutes or until shrimp are opaque and corn is tender.
Remove from oven.
Garnish with parsley and serve.