Step 1: Preheat your oven to 400°F (200°C) and lightly grease a 9x13 inch baking dish.
Step 2: In a large skillet over medium-high heat, brown the ground beef with the diced onions and bell peppers until the meat is no longer pink.
Step 3: Drain any excess grease from the skillet and season the beef mixture with garlic powder, salt, and pepper.
Step 4: In a medium bowl, whisk together the cream of mushroom soup, sour cream, and milk until smooth.
Step 5: Stir the soup mixture, corn, and black beans into the skillet with the beef until well combined.
Step 6: Spread the beef mixture evenly into the bottom of the prepared baking dish.
Step 7: Sprinkle 1.5 cups of the shredded cheddar cheese over the beef layer.
Step 8: Arrange the frozen tater tots in a single, even layer across the top of the cheese.
Step 9: Bake for 30 minutes. Remove from the oven, sprinkle the remaining 0.5 cup of cheese over the tots, and bake for an additional 5 minutes until the cheese is melted and tots are crispy.