Preheat the grill to medium-high heat.
Grill the corn over medium heat for about 10 - 12 minutes, flipping often until the kernels are slightly toasted and charred.
Meanwhile prepare the shallot dressing by combining in a large bowl, the sliced shallots, olive oil, rice wine vinegar, salt, pepper, chili powder. Stir until combined.
Cut the corn off the cob with a sharp knife.
Add the corn kernels to the bowl with the dressing. Add the jalapenos, Fresno chili peppers, basil, feta cheese and avocados and toss to coat with the dressing.