Preheat the oven to 400°F (200°C).
Toss diced sweet potatoes with olive oil, salt, and pepper on a baking sheet. Roast for 25 minutes or until tender and slightly crispy at the edges.
Meanwhile, season chicken breasts with salt and pepper. Cook in a skillet over medium heat for 6-7 minutes per side or until cooked through.
Brush BBQ sauce onto the chicken and let it simmer for 1-2 more minutes. Slice the chicken once it's slightly cooled.
Divide the greens between bowls. Top with roasted sweet potatoes, sliced BBQ chicken, corn, black beans, avocado, and red onion.
Drizzle with more BBQ sauce and ranch or Greek yogurt if using. Serve warm.