Brown ground chuck with garlic in a pot over medium-high heat. Add tomato sauce, Rotel, salt, oregano, cumin, and chili powder. Cover and reduce heat to low. Simmer for 30 minutes.
Add drained and rinsed beans. Stir to combine, then cover and simmer for another 20 minutes.
Mix masa with water, then add to the chili. Stir to combine and simmer for a final 10 to 15 minutes. Set aside.
Serve by slicing the Frito bags open lengthwise. Pile in chili and cheese, and diced onion if using. Serve immediately with plastic forks. A crowd-pleaser!