In a screw-top jar combine the 1/2 cup oil, lemon juice, mint, garlic, and 1/2 teaspoon each salt and pepper; cover and shake until combined.
To grill corn, pull back husks, but don't remove. Remove silks; rinse corn. Brush with olive oil and sprinkle lightly with salt and pepper. Fold husks back around corn. Tie tops of husks closed with 100-percent-cotton kitchen string.