Preheat your grill or grill pan to high heat. Brush the corn cobs lightly with vegetable oil to prevent sticking and promote even charring.
Place the corn directly on the hot grill, turning every 2-3 minutes. Grill until evenly charred with blackened spots and tender kernels, about 10-12 minutes. You should hear a gentle sizzle and see consistent blackened patches.
While the corn is grilling, combine mayonnaise, lime juice, minced garlic, chili powder, and a pinch of salt in a small bowl. Mix until smooth and well combined. The mixture should be creamy with a slightly spicy aroma.
4 ears corn on the cob
Once the corn is grilled and slightly cooled for handling, hold each cob with tongs and brush generously with the prepared sauce using a basting brush. Ensure an even coating of the smoky, creamy mixture on all sides.
4 ears corn on the cob
Sprinkle the crumbled cotija cheese over the coated corn while the sauce is still moist, allowing it to stick. The cheese should appear fluffy and white, contrasting with the charred kernels.
4 ears corn on the cob
Transfer the finished corn to a serving platter. Garnish with additional chili powder and a squeeze of lime for extra flavor. Serve immediately while hot and smoky.