Place corn in a large stockpot; add water to cover. Bring to a boil. Cook, covered, until crisp-tender, 6-8 minutes; drain. Cool slightly. Cut corn from cobs and place in a large bowl. Stir in red pepper, tomatoes and onion.
In a small bowl, whisk dressing ingredients until blended. Pour over corn mixture; toss to coat. Refrigerate, covered, at least 1 hour.