If using ears of corn, cut the kernels off and set aside. Discard the cobs.
Heat the oil in a large skillet over medium heat. Add the onions and cook, stirring occasionally, until softened, about 2 minutes. Add the garlic and cook for 1 minute more. Stir in the corn, lima beans, zucchini, and tomatoes and cook, stirring occasionally, until the vegetables are tender, about 7 minutes.
Spray a large nonstick skillet or grill pan with cooking spray, and preheat it over medium-high heat.
In the meantime, prepare the scallops. Pat them dry and season them with 1/4 teaspoon of salt and 1/4 teaspoon of pepper. Add the scallops and cook until the inside is opaque, 5 to 6 minutes, turning once.
Stir the vinegar and basil into the succotash, season with additional salt and pepper, to taste, and serve topped with grilled scallops. Garnish with Parsley Drizzle.