Preheat oven to 400°F (200°C) and line a large baking sheet with parchment paper.
In a large mixing bowl, combine ground beef, panko breadcrumbs, beaten egg, 1/2 cup barbecue sauce, garlic powder, salt, and pepper. Mix until just combined.
Form the beef mixture into 1-inch meatballs (approximately 16-20 units) and place them on one half of the prepared baking sheet.
Arrange broccoli florets and corn on the remaining half of the baking sheet, seasoning lightly with salt and pepper.
Roast in the oven for 15 minutes. Remove the pan, brush the meatballs with the additional 1/4 cup barbecue sauce, and return to the oven for 8-10 minutes until meatballs reach an internal temperature of 160°F.
Prepare the sauce by placing avocado, Greek yogurt, lime juice, cilantro, garlic, and water into a high-speed blender. Process until smooth and emulsified.
Assemble bowls by partitioning the cooked rice, roasted vegetables, and meatballs into four portions. Drizzle each bowl generously with the avocado goddess sauce.