In a skillet, heat olive oil, and brown the beef breaking it up with a wooden spoon as it cooks. Season with salt and pepper and cook until it’s no longer pink. Drain fat if there’s a lot of grease.
Add the onion, and cook for 2-3 more minutes until it’s translucent.
Add a can of ROTEL, and season with taco seasoning. Cook for 2-3 more minutes, the juices will evaporate. Remove from heat, and stir in the pinto beans.
Preheat the oven to 350°F/180°C, and grease a 9x13inch dish.
Add the beef mixture to the greased dish in an even layer, top with frito chips and sprinkle with cheese.
Bake for 15 minutes or until the cheese has melted.
Top with shredded lettuce, tomato, sour cream, and jalapeno slices.
If you are making this more than 15 minutes ahead of time, wait to add the vegetables until right before serving. If you aren’t sure that the whole casserole will be eaten, you may want to serve the lettuce and other cold toppings on the side.
If you can’t find ROTEL: You can substitute with 10 ounces of petite diced tomatoes plus a teaspoon or more of canned diced chiles.