Preheat the oven to medium high heat (approximately 350-375 degrees F).

Cut 4 large pieces of heavy duty foil into approximately 12X12 inches and spray the foil into non-stick cooking spray.

In a large mixing bowl, gently toss together half of the olive oil, half of the salt and pepper, squash, zucchini, bell peppers and onions until the veggies are coated.

Divide the vegetables evenly and place them on the center of each piece of foil.

Place a fish fillet in the center of each foil packet on top of the vegetables.

Drizzle the remaining olive oil evenly over the fish fillets and seasoning with the remaining salt, pepper, Italian seasoning, garlic powder and red pepper flakes (if using).

Top with lemon slices.

Fold up the edges of the foil around the vegetables and fish to create a closed packet.

Place the foil packets on the grill over direct heat.  Grill for 8-10 minutes (flipping halfway through the cook time) until the veggies are tender and the fish flakes easily.

Let the packets sit for about 5 minutes to cool off slightly and then they are ready to serve topped with the fresh parsley and enjoy!