Preheat oven to 400 degrees.
In a saute pan, add the oil, scallions and onion. Saute until the onions are translucent. Add the garlic and saute for just 1 minute more. Remove from heat.
Meanwhile, add the sliced zucchini and yellow squash to a microwave safe bowl and cook for 3-4 minutes or until the squash is par-cooked.
Par-cook the corn and pearl onions in the same manner.
Add the cooked onions to the bottom of the pie dough and top with a layer of the vegan mozzarella and vegan parmesan.
Layer the zucchini and yellow squash. Top with the corn and pearl onions.
Finish with another layer of each of the two cheeses and parsley (or other herbs as desired). Season with salt and pepper.
Bake for about 30-40 minutes or until the crust is golden and the squash tender.