Bring a large pot of salted water to a boil and cook the rotini until al dente according to the package directions. Drain the pasta, rinse under cold water to stop the cooking process, and let it cool completely before assembling the salad.

Season the chicken thighs generously with your favorite BBQ rub and grill over medium-high heat until they reach an internal temperature of 175–185°F for juicy, flavorful chicken. Let the chicken rest for 5–10 minutes before dicing it into bite-sized pieces.

In a large mixing bowl, combine the cooled pasta, diced grilled chicken, cooked bacon, shredded Colby Jack cheese, half of the sliced green onions, and about half of the homemade ranch dressing. Toss everything together until evenly coated, adding more ranch as needed to reach your preferred consistency.

Taste the pasta salad and adjust with additional ranch dressing or seasoning if desired. Cover and refrigerate for at least 30 minutes before serving to allow the flavors to meld together.

If serving immediately with lettuce, fold the shredded lettuce into the pasta salad along with the remaining green onions and additional ranch dressing just before serving. This keeps the lettuce crisp and fresh while adding extra texture.

Serve chilled and garnish with extra green onions, bacon, or shredded cheese if desired. For the best make-ahead results, prepare the pasta salad in advance and wait to add the lettuce until just before serving so it stays crisp.