Step 1

Preheat the oven to 350 degrees F (175 degrees C). Spray a large casserole dish with cooking spray.

Step 2

Bring a large pot of lightly salted water to a boil. Add penne and cook, stirring occasionally, until tender yet firm to the bite, about 11 minutes. Drain.

Step 3

While the pasta is cooking, melt butter in a large skillet over medium heat. Add onion and bell pepper and cook, stirring occasionally, until vegetables are tender, about 5 minutes. Add mushrooms and cook until they release their liquid, about 5 minutes. Add garlic and cook, stirring occasionally, until fragrant, about 1 minute.

Step 4

Stir in processed cheese food, diced tomatoes and juice, diced tomatoes and green chiles with juice, and mild chile peppers. Cook and stir until cheese has melted, 5 to 10 minutes. Remove from heat and stir in cooked pasta and chicken. Pour into the prepared baking dish.

Step 5

Bake in the preheated oven until heated through, about 20 minutes. Serve warm.