Preheat the oven to 350°F (175°C). Lightly spray a 9x13-inch baking dish with cooking spray.
In a large mixing bowl, combine the softened cream cheese and undrained Rotel; stir until smooth.
Add the chopped cooked chicken, shredded Mexican cheese, cumin, chili powder, minced garlic, oregano, and black pepper; mix until evenly combined.
Spread the mixture evenly into the prepared 9x13-inch baking dish.
Bake for 30 minutes, or until the dip is bubbly and heated through.
Remove from the oven and serve warm with tortilla chips or Fritos.