In a small skillet, add the olive oil and chicken pieces and saute for 5 to 7 minutes, or until cooked through. Season with a little salt and pepper.
Cook the pasta to al dente. (It will take on a little more liquid as it bakes, so don't over-boil it!)
While the pasta is cooking, prepare the homemade creamy-cheesy sauce in a large skillet or saucepan. Melt the butter, whisk in the flour and quickly whisk in the milk to prevent from clumping. Bring to bubbling over medium-low heat, stirring often. Once it begins to thicken, stir in the garlic powder, Parmesan cheese and shredded mozzarella cheese. Then add the mushrooms and sun-dried tomatoes. Let simmer for 3 to 4 minutes, then season to taste.
Preheat the oven to 350 degrees. Lightly spray a 9x13-inch glass baking dish with non-stick cooking spray. Add the cooked pasta and cooked chicken to the baking dish, then pour the cheesy sauce over the top. Gently mix it in and let the sauce fill in around the pasta and chicken.
Bake in the preheated oven for 20 minutes.
Serve Sun-Dried Tomato and Parmesan Bake with side of veggies.