In 10-inch skillet, cook beef over medium-high heat 5 to 7 minutes, stirring occasionally, until thoroughly cooked; drain.
Add cooking sauce, peanut butter, chocolate chips and taco seasoning mix. Heat to boiling, stirring frequently. Reduce heat; simmer 5 minutes, stirring occasionally.
Meanwhile, heat taco shells as directed on package. Serve taco shells with beef mixture, lettuce, tomato and cheese.