Cook pasta according to package instructions; drain and set aside.

In a large skillet, heat olive oil over medium heat. Add the chicken pieces, season with salt and pepper, and cook until golden brown and cooked through. Remove chicken and set aside.

In the same skillet, add the bacon and cook until crispy. Remove bacon and set aside on a paper towel to drain.

Remove most of the bacon fat from the skillet, leaving about 1 tablespoon. Add the diced onion and garlic to the skillet, and sauté until softened.

Lower the heat and add the ranch dressing, milk, and half of the shredded cheese. Stir until the cheese melts and the sauce is smooth.

Return the cooked chicken and bacon to the skillet. Add the cooked pasta and toss to combine. If the sauce is too thick, add a little more milk to reach desired consistency.

Season with salt and pepper to taste. Garnish with the remaining cheese and chopped parsley before serving.