Place individual ears of corn on a sheet of foil. Drizzle with olive oil, a pinch each of salt, pepper, garlic powder, and chili powder. Squeeze about a teaspoon of lime juice over corn. Give the corn a rub with the oil and seasonings. Wrap in foil. Repeat with each ear of corn, wrapping each ear individually.
Rub the jalapeno with olive oil.
Place foiled corn and jalapeno on a grill over high heat. Rotate corn every 3-4 minutes (cooking time may be longer for tougher, out of season corn).
Cook the jalapeno until entire pepper is charred and black. Remove jalapeno from the grill; place in a small bowl covered with plastic wrap. Let set 3-4 minutes. Remove from bowl; remove charred skin (use a paper towel to help). Remove seeds; dice jalapeno. Set aside until ready for use.
When corn is cooked, remove from grill; let cool slightly.
Remove foil from corn.
Use a corn skewer to stand corn up on one end; cut corn kernels off cob (Note: Cut corn on a sheet pan with raised edges to contain corn).
In medium-size bowl, whisk mayo, lime juice, cilantro, cotija, green peppers and diced jalapeno.
Stir in corn. Top with additional cotija and cilantro.