Bring 2 cups of water to boil. Add in quinoa and reduce to a simmer. Cover and let cook for 15 minutes until water is absorbed. Transfer to a large bowl to cool slightly.
Into the bowl with the quinoa, add in the beans, cucumber, celery, bell pepper, tomato, and red onion.
Add the lemon juice, olive oil, garlic powder, and kosher salt. Toss well. Serve immediately or cover and refrigerate for later.
Video
Notes
Make-ahead instructions: this entire dish can be made ahead and stored in an airtight container in the refrigerator for up to a week.