Brush or rub each cob with some canola oil and sprinkle with salt and pepper. Place the corn on the hot grill and char each side, 2 to 3 minutes per side. You want the corn to get great char marks! Once the corn has charred, set aside until cool enough to handle. Once the corn has cooled, stand each ear up, stalk end down, in a wide, shallow bowl and, using your knife, slice the corn kernels off the cob.
Meanwhile, make the vinaigrette. In a food processor, add the basil and garlic and pulse until the basil starts to break down. Add the vinegar. Continue pulsing while adding the oil in a steady stream and process until smooth. Season with salt and pepper.
In a large mixing bowl, combine the corn, tomatoes and red onion. Drizzle the basil vinaigrette over the salad and toss to combine. Season with salt and pepper.