In a mixing bowl, blend together Greek yogurt, chives, dill, garlic powder, onion powder, parsley, and a pinch of salt. Gradually stir in water until the dressing reaches a smooth, pourable consistency. Allow the dressing to rest for 20 to 30 minutes at room temperature.

Preheat your grill to medium-high heat, around 400°F. Place the corn directly on the grill grates and cook for about 5 minutes on each side, or until char marks appear.

Toss shishito peppers onto the grill for the last 5 minutes of corn's cooking time, turning occasionally until the skin blisters.

After cooling, carefully cut the kernels off the cob and slice the grilled peppers. Chop halved cherry tomatoes and ripe avocado.

In a large mixing bowl, combine the grilled corn, shishito peppers, cherry tomatoes, soaked red onion, and avocado. Gently toss to mix.

Season with salt and pepper, drizzle with Greek yogurt ranch dressing, and toss gently to coat. Serve immediately.