Preheat the oven to 425 degrees Fahrenheit.

Add the ground beef, chopped pepper, and onion to a large skillet and cook on stovetop over medium/high heat until the meat is no longer pink, breaking it up with a spatula as it cooks.

Add the taco seasoning, water, and ¼ cup taco sauce to the skillet and stir until all ingredients are fully combined. Reduce the heat to low and allow the meat mixture to simmer while you prepare the pasta.

Bring a large pot of water to a boil on the stovetop over medium/high heat. Add the pasta to the pot and allow it to boil for about 12 minutes or until al dente. Strain the water from the pasta and set the pasta aside.

Spread ½ cup taco sauce into the bottom of a 9x13-inch baking dish and arrange 20 of the pasta shells on top of the sauce.

Divide the meat mixture evenly into each of the pasta shells, using a spoon to stuff the shells.

Drizzle the queso and the remaining ½ cup of taco sauce evenly over the top of the stuffed shells.

Sprinkle the shredded cheese evenly over the top of the stuffed shells.

Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. Remove the foil and cook for an additional 6 minutes.

Serve topped with sour cream, lettuce, tomatoes, or extra queso sauce.