Bring a large pot of salted water to a boil and cook the penne according to package directions until al dente. Drain and set aside.
While the pasta cooks, heat the olive oil in a large skillet over medium heat.
Add the chicken pieces and diced red onion to the skillet and sauté, stirring occasionally, until the chicken is browned and cooked through (no longer pink inside), about 6–8 minutes.
In a large bowl, whisk together the barbecue sauce and sour cream until smooth, then stir in the shredded mozzarella and cheddar cheeses.
Add the hot cooked pasta to the sauce and toss to coat evenly.
Fold in the cooked chicken and onions, then add the corn, rinsed black beans, halved cherry tomatoes, and chopped lettuce; toss gently to combine.
Serve the pasta salad immediately.