Preheat an outdoor grill for medium heat; lightly oil the grate.
Cook the corn on the preheated grill, turning occasionally, until the corn is tender and specks of black appear, about 10 minutes; set aside until just cool enough to handle. Slice the kernels off of the cob and place into a bowl.
Combine the warm corn kernels with the red/green pepper, diced tomato, onion, cilantro, and olive oil. Season with salt and pepper; toss until evenly mixed. Set aside for at least 30 minutes to allow flavours to blend before serving.