Bring 6 cups water to a boil in a large pot. Add the 2 cups dried pasta and cook until tender, about 11 minutes (follow package directions).
Drain the pasta in a colander and return to the pot or a large bowl; toss with 1/2 tablespoon olive oil to prevent sticking. Let cool to room temperature, then chill in the refrigerator until fully cooled, about 20 minutes.
In a large bowl, combine 1 cup Greek yogurt and 1/2 cup mayonnaise. Whisk in 2 tablespoons ranch dry mix, 1 teaspoon dried parsley (or 2 Tbsp fresh), 1/4 teaspoon salt, and 1/4–1/2 teaspoon black pepper.
Add the chilled pasta, 1/2 rotisserie chicken (about 2 cups cubed), 4–6 chopped green onions, 1 cup shredded Colby Jack, and 1 cup peas to the dressing. Toss until everything is evenly coated.
Cover and refrigerate the pasta salad until very cold, at least 30 minutes. Taste and adjust seasoning or mayonnaise if desired before serving.
