You can either serve this as a salad, or as a salsa with tortilla chips. Fresh corn off the cob is best, although you can use thawed frozen corn if it is not in season. But for the love of all that is holy, please not use canned corn. Ick!
Mix corn, tomatoes, onion, jalapeno pepper, and cilantro together in a bowl.
Whisk olive oil, and lime juice together in a small bowl; drizzle over the corn salad. Season salad with salt and pepper.
Cover bowl with plastic wrap and refrigerate at least 30 minutes.
Add avocado prior to serving to avoid browning.