Preheat a very clean outdoor grill to high heat and lightly oil grates.
Grill the corn, turning occasionally, until it's charred and cooked through, about 10 minutes total.
Once cooled a bit, cut the corn off the cob and place kernels in a large serving bowl.
Add the tomatoes, garlic, bell peppers, avocado, jalapeƱo pepper, cilantro, lime juice, sea salt, and pepper, then gently combine.
Crumble feta ontop if desired to serve.