In a small pot, combine rice and chicken broth. Bring to a boil, then reduce heat to low, cover, and simmer for 15-18 minutes until liquid is absorbed. Fluff with a fork.
Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a large bowl, combine ground beef, breadcrumbs, egg, minced onion, minced garlic, oregano, parsley, salt, and pepper. Mix until just combined.
Form the meat mixture into approximately 16 small meatballs (about 1.5 inches in diameter) and place on the prepared baking sheet.
Bake meatballs for 15-20 minutes or until the internal temperature reaches 160°F (71°C).
Prepare tzatziki by mixing Greek yogurt, grated and drained cucumber, lemon juice, and olive oil in a small bowl. Season with salt to taste.
Assemble the bowls by dividing the cooked rice equally among four bowls.
Top each bowl with four meatballs, cherry tomatoes, sliced cucumbers, sliced red onion, and Kalamata olives.
Garnish with a dollop of tzatziki and a sprinkle of crumbled feta cheese before serving.