Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a large bowl, toss the diced sweet potatoes with olive oil, garlic powder, paprika, salt, and pepper until evenly coated. Spread them out in a single layer on the prepared baking sheet.
Roast the sweet potatoes in the preheated oven for 25-30 minutes, or until they are tender and slightly caramelized, stirring halfway through.
While the sweet potatoes are roasting, season the chicken breasts with salt and pepper. Heat a grill pan or outdoor grill over medium-high heat.
Grill the chicken for about 6-7 minutes per side, or until fully cooked and the internal temperature reaches 165°F (75°C). Brush the chicken with BBQ sauce during the last few minutes of cooking.
Remove the chicken from the grill and let it rest for 5 minutes before slicing it into strips.
To assemble the bowls, divide the cooked brown rice or quinoa among four bowls. Top each bowl with roasted sweet potatoes, grilled chicken, corn, and sliced avocado.
Drizzle additional BBQ sauce over the top if desired and garnish with chopped cilantro. Serve with lime wedges on the side.