Fill a medium saucepan with water, bring to a boil, and season generously with kosher salt. Add the shucked corn and cook for 5 minutes. Meanwhile prepare a large bowl with iced water.
Drain the corn and cool in the iced water for a few minutes. Turn over a few times with a spoon or tongs, if desired. Removed from the ice bath and drain on paper towels and pat dry.
Place the sliced red onion in a colandar or fine mesh sieve. Place the onion in the iced water in the same bowl as the corn for 10 minutes to remove the harsh bite. Drain and pat dry.
Place a piece of parchment paper in a sheet pan. Place a cutting board on top. Stand the corn cob upright and holding firmly, cut the kernels off the cobs with a sharp chef's knife. Place the kernels in a large bowl.
Add the sliced onion, tomatoes, and peaches to the corn.
Drizzle the vinegar of choice and the extra virgin olive oil, the herb, and salt and pepper. Gently toss with a large spoon. Taste for seasoning and adjust.
Add the crumbled feta on top. Cover the salad tightly. Place in fridge until ready to serve.
If desired, spoon salad into individual jars. Keep in fridge until ready to transfer to picnic.