Start by preparing all of your vegetables. Dice the bell peppers, red onion, and finely chop the cilantro. Rinse and drain the beans and corn.
In a large mixing bowl, combine the black beans, corn, diced bell peppers, red onion, tomatoes, and cilantro. Gently toss until everything is evenly distributed.
In a small bowl or jar, whisk together the olive oil, lime juice, red wine vinegar, garlic, salt, and pepper until well combined. Taste and adjust seasoning as needed.
Pour the dressing over the bean and vegetable mixture and toss gently to coat. Add diced avocado last, folding it in carefully to avoid mashing.
Cover and refrigerate for at least 20–30 minutes before serving to allow the flavors to meld. Serve chilled as a dip with tortilla chips or as a topping for grilled chicken, fish, or salads. Store leftovers in an airtight container in the refrigerator for up to 3 days.
