Preheat the oven to 375F. Spray a baking dish with oil.
Boil up a large pot of water. When the water is boiling, add in the diced chicken and broccoli florets. Boil them for around 5 minutes until the broccoli is tender and the chicken has cooked.
Drain the water and set the broccoli with chicken aside.
In a large bowl, combine cream cheese with mayonnaise, ½ cup grated cheddar, garlic powder, onion powder, salt, and black pepper.
Mix cooked chicken and steamed broccoli with the cheese mixture inside the baking dish. Level it out.
Sprinkle with the remaining ¼ cup of cheddar cheese.
Bake for 15 minutes and then broil for 2-3 minutes until the cheese goldens up.
