Remove husks and silks from corn. Brush corn with 2 tablespoons olive oil. For a charcoal grill, place corn on the grill rack directly over medium-hot coals. Grill uncovered for 10 to 15 minutes or until browned, turning frequently to prevent overbrowning. (For a gas grill, preheat grill. Reduce heat to medium-high. Place corn on grill rack over heat. Cover and grill as above.) When cool enough to handle, cut kernels off the cobs.
In a large bowl, combine corn, tomatoes, red onion, rice vinegar, 2 tablespoons olive oil, the salt, and pepper. Serve at room temperature, or cover and chill for up to 24 hours before serving.