Preheat grill to 350 to 400 (medium-high). Lightly coat corn cobs with cooking spray.
Sprinkle with salt and pepper.
Grill corn, covered with grill lid, 15 to 20 minutes or until golden brown, turning every 5 minutes.
Remove from grill; cool 15 minutes.
Hold each grilled cob upright on a cutting board; carefully cut downward, cutting kernels from cob. Discard cobs; place kernels in a large bowl. Gently stir in tomatoes and next 5 ingredients. Cover and chill until ready to serve, if desired.
If chilled, let corn mixture stand at room temperature 30 minutes. Peel and chop avocados; toss with corn mixture just before serving.
