If you haven't already cooked your quinoa or rice, start that first according to package directions. While the grain cooks, season both sides of the chicken breasts generously with garlic powder, onion powder, paprika, salt, and pepper. If chicken breasts are thick, pound them to a uniform 3/4-inch thickness throughout for even cooking.

Heat olive oil in a large skillet over medium-high heat until shimmering. Add chicken and cook undisturbed for 6-7 minutes until golden-brown on the bottom. Flip once and cook another 6-7 minutes until internal temperature reaches 165°F. Remove from heat and let rest for 5 minutes before slicing.

While chicken rests, whisk together Greek yogurt, mayonnaise, BBQ sauce, ranch seasoning, and milk in a small bowl until completely smooth. The mixture should drizzle off a spoon but not be watery. Add more milk if needed. Taste and adjust salt and pepper.

Divide cooked quinoa or brown rice among 4 bowls. Slice rested chicken against the grain into strips. Top each bowl with sliced chicken, cherry tomatoes, cucumber, red onion, corn, and avocado slices. Drizzle generously with BBQ ranch dressing and garnish with fresh cilantro.