Heat olive oil in a large skillet over medium heat. Add diced onion and cook 3-4 minutes until softened. Stir in minced garlic for 30 seconds.
Add ground beef and cook, breaking it up, until no longer pink (5-7 minutes). Drain excess fat if needed.
Stir in taco seasoning, salt, pepper, and water/broth. Simmer 3-5 minutes until slightly thickened.
Warm the cooked rice. Gently warm beans and corn if desired.
Divide rice among 4 bowls. Top with seasoned beef, beans, corn, lettuce, tomatoes, avocado, and cheese.
Finish with sour cream, cilantro, lime juice, and any other toppings. Serve immediately.