Preheat oven to 350 degrees. Spray a 9X13 inch baking dish with nonstick cooking spray; set aside.
Cook the pasta, in well-salted water according to package instructions. Drain pasta and dry out the pasta pot. Return pasta to pot.
In a medium mixing bowl, toss chicken with 1 ½ teaspoons salt and 1/2 teaspoon black pepper until pieces are evenly coated.
In a large skillet, heat 2 tablespoons oil. When hot, add chicken in batches, allowing pan bottom to be visible between pieces, and brown on all sides. Remove chicken to a plate; set aside. Repeat with the remaining chicken and add more oil if needed.
Add 2 tablespoons of oil to skillet and saute onions and garlic, over medium-low heat until tender, about 5 minutes. Stir in oregano, cumin, chili powder, and coriander and continue to saute until spices are fragrant about 1 minute.
In a medium bowl, stir together Rotel, chicken soup, sour cream, and milk until evenly combined.
Add chicken, onion mixture and soup mixture to pasta and toss well to combine. Pour into the prepared baking dish and sprinkle the top with Pepper Jack. Place in preheated oven and cook until sauce is bubbly and cheese is melted about 30 minutes.