Cut the kernels off the cob, cutting close to the cob.
In a large bowl, toss the corn with the red onions, red peppers and basil (if making ahead of time leave out the basil).
In a liquid measuring cup or small bowl, combine the olive oil, vinegar, salt and black pepper. Whisk until blended, then pour it over the salad. Toss to combine.
Taste for seasonings, serve immediately.
If you’re making it ahead, add fresh basil right before serving.