Preheat the grill or grill pan over medium-high heat.
In a mixing bowl, combine the olive oil, garlic powder, onion powder, salt, and black pepper. Rub the mixture evenly over the chicken breasts.
Place the chicken on the grill and cook for about 6-7 minutes on each side, or until the internal temperature reaches 165°F (75°C). Remove from the grill and let rest for a few minutes.
While the chicken is grilling, bring a pot of water to a boil, then add the broccoli. Steam the broccoli for about 4-5 minutes until tender but still bright green. Drain and set aside.
In a separate mixing bowl, whisk together the mayonnaise, Greek yogurt, minced garlic, and lemon juice until smooth. Adjust seasoning if necessary.
Slice the grilled chicken into strips.
To assemble the bowls, divide the steamed broccoli among four bowls, add the sliced grilled chicken on top, and drizzle with the creamy garlic sauce. Garnish with fresh parsley.