Fill a large pot with water and add the Old Bay seasoning, lemon halves, and onion.
Bring the water to a boil over high heat.
Add the potatoes to the boiling water and cook for 10-12 minutes.
Once the potatoes are tender, add the corn and cook for an additional 5 minutes.
Reduce heat to medium and add the shrimp to the pot.
Cook the shrimp for about 3-5 minutes until they turn pink and opaque.
Carefully drain the pot, reserving some broth if desired.
Spread the shrimp, potatoes, and corn on a large serving tray.
Garnish with fresh parsley and serve with extra lemon wedges.
Enjoy your shrimp boil with friends and family!