Preheat your grill or grill pan over medium-high heat. While it heats, season the chicken breasts with olive oil, garlic powder, onion powder, salt, and pepper.
Grill the chicken for about 6-7 minutes per side, or until the internal temperature reaches 165°F. Remove from the grill and let it rest for 5 minutes before slicing.
While the chicken is resting, steam the broccoli florets until tender, about 4-5 minutes. You can use a steamer basket or microwave with a splash of water in a covered bowl.
In a small bowl, mix together the Greek yogurt, mayonnaise, minced garlic, lemon juice, salt, and pepper to create the creamy garlic sauce. Adjust seasoning to taste.
To assemble the bowls, divide the steamed broccoli among four bowls, top with sliced grilled chicken, and drizzle with the creamy garlic sauce.