In a large mixing bowl, combine the cannellini beans, chickpeas, sun-dried tomatoes, red onion, and parsley.
In a separate small bowl, whisk together the olive oil, red wine vinegar, garlic powder, salt, black pepper, and crushed red pepper flakes if using.
Pour the dressing over the bean mixture and gently toss until everything is well coated.
Cover the bowl with plastic wrap or a lid and refrigerate for at least 30 minutes to allow the flavors to meld.
Serve chilled or at room temperature, and enjoy!