In a medium skillet over medium heat, brown ground sirloin, breaking up chunks with a wooden spoon, until no pink remains, 4 to 5 minutes. Stir in beans and taco seasoning. Reduce heat to low and cook, stirring occasionally, until flavors have blended, about 10 minutes. Using a slotted spoon, transfer mixture to a bowl; let cool for 10 minutes.
Toss lettuce, onion, Cheddar and salad dressing in a large bowl. Toss in meat mixture until just combined. Divide salad among 6 plates, top with crumbled chips and serve.