You can cook and peel the shrimp early in the day, then cover and chill. You can also make the marinade in the morning, but don't combine the two components until about 45 minutes to one hour before you expect your guests to arrive.
12 cups water
2 pounds unpeeled medium shrimp
2 teaspoons Old Bay seasoning
1 cup chopped onion
1 cup chopped green bell pepper
2/3 cup cider vinegar
1 1/2 tablespoons vegetable oil
1 teaspoon salt
1/4 teaspoon black pepper
How to Make It
Bring water to a boil in a large saucepan. Add shrimp and seasoning; cook 3 minutes or until done. Drain and cool completely. Place shrimp in a large zip-top plastic bag. Add remaining ingredients; seal and marinate in refrigerator 30 minutes, turning bag occasionally. Remove shrimp from bag, reserving marinade. Peel shrimp; place in a large bowl. Add reserved marinade; toss gently to coat.