Prep the oven. Preheat your oven to 400°F (200°C) with a rack positioned in the center.
Make the chili. In a large saucepan, heat the olive oil over medium-low heat. Then, add the diced onion, chili powder, garlic powder, ground cumin, salt, and pepper. Cook for about 5 minutes until the onion is soft and fragrant. Next, add the ground beef, breaking it up as it cooks until browned (about 8-10 minutes). If there is a lot of extra grease, drain some off. Once the beef browns, stir in the diced tomatoes and rinsed beans. Simmer uncovered for 15 minutes until the chili thickens. The consistency should be hearty and stew-like, not watery.
Assemble the casserole. Pour the chili mixture evenly into the casserole dish. Then, sprinkle the frozen shredded hash browns on top of the chili in an even layer. Season the potatoes lightly with a pinch of salt. Finally, top the potatoes with the shredded cheddar cheese.
Bake the casserole. Place the casserole in the oven and bake for 30-40 minutes until the chili is bubbling and the cheese is melted. For a golden, crispy top, broil on low for 3-5 minutes. Keep a close eye to prevent burning.
Serve. Let the casserole rest for 5 minutes after removing it from the oven. Scoop and serve immediately. Enjoy!