In 10-inch skillet, cook beef over medium-high heat 5 to 8 minutes, stirring frequently, until beef is thoroughly cooked; drain.
In 5- to 6-quart slow cooker, place cooked beef and remaining Taco Pasta ingredients except pasta shells and Cheddar cheese; stir until well combined.
Cover; cook on Low heat setting 4 to 5 hours.
About 15 minutes before serving, cook and drain pasta as directed on package. Uncover slow cooker; stir in pasta and shredded Cheddar cheese until well combined.
Cook uncovered on High heat setting 10 to 15 minutes longer or until cheese is melted.
Serve topped with sour cream, salsa and/or shredded cheese.