Preheat an outdoor grill or grill pan to medium-high heat.
Brush husked corn with a little olive oil.
Grill corn for 8–10 minutes, turning every 2 minutes, until kernels are tender with char marks.
Remove corn and let cool until easy to handle.
Dice avocados, halve cherry tomatoes, thinly slice red onion, and chop cilantro.
Stand each cooled ear of corn upright and slice kernels off into a large bowl.
Add diced avocado, halved cherry tomatoes, sliced red onion, and chopped cilantro to the bowl.
In a small bowl, whisk together olive oil, fresh lime juice, salt, and black pepper.
Pour dressing over salad ingredients and gently toss to coat.
Taste and adjust salt or pepper if needed, then serve immediately.