Brown the ground beef in a skillet over medium-high heat until no longer pink, then drain any excess fat. This step helps keep the slow-cooker soup from tasting greasy.

Add browned, drained ground beef, black beans, kidney beans, corn, Rotel tomatoes, diced tomatoes, taco seasoning, ranch dressing mix, and beef or chicken broth to the crockpot, then stir to combine. Make sure everything is evenly mixed so the seasoning disperses.

Cook on Low for 6–8 hours (or High for 3–4 hours) with the lid on. The soup will develop a deep Tex-Mex flavor and thicken as it cooks.

If the soup becomes too thick, add extra broth a splash at a time and stir until it reaches your preferred consistency. Check near the end of cooking so it stays hot and properly seasoned.

Taste the soup and adjust seasoning before serving. This ensures the final flavor matches your preference.

Serve with cheddar, sour cream, tortilla chips, sliced green onions, jalapeños, and avocado. Add toppings right before eating for the best crunch and freshness.