Heat a large pot or Dutch oven over medium-high heat. Add cooking oil and let it warm for 30 seconds.
Add ground beef, diced onion, and minced garlic to the pot. Break up the meat as it cooks into small crumbles. Cook for 7-8 minutes until beef loses all pink color and onions are translucent and soft. Drain excess grease if needed, leaving about 1 tablespoon.
Add diced bell pepper, Rotel tomatoes, cream cheese, and taco seasoning. Stir everything together and cook for 4-5 minutes until tomatoes soften and cream cheese begins to melt.
Pour in beef broth and stir well to combine. Reduce heat to low-medium to maintain a gentle simmer (not a rolling boil).
Let the soup simmer for 15-20 minutes, stirring occasionally to prevent sticking. The soup will thicken as it cooks and flavors will meld together.
Taste and adjust seasoning with salt and pepper as needed. Add more broth if too thick, or simmer uncovered longer if too thin.
Ladle into bowls and serve with your favorite toppings: diced avocado, shredded cheese, cilantro, lime juice, sour cream, and crushed tortilla chips.