Preheat your grill to medium-high heat, aiming for about 425°F.

Cut eight sheets of heavy-duty aluminum foil into 12 x 14-inch pieces.

In a large mixing bowl, combine chopped zucchini, yellow squash, whole grape tomatoes, diced green bell pepper, sliced red onion, fresh corn, and raw shrimp.

Drizzle with olive oil and sprinkle with garlic, salt, black pepper, paprika, celery seed, thyme, and cayenne. Toss until well-coated.

Layer two sheets of foil per packet, placing one sheet perpendicular to the other. Spoon the mixture into the center.

Fold the edges of the foil over the mixture to create a tight seal.

Cook the sealed packets on the preheated grill for 12 to 14 minutes, turning halfway through.

Remove the packets from the grill and garnish with minced parsley and lemon wedges.