Bring a saucepan of water to a boil and lower to a simmer. Add the chicken breasts and cook through.
Let the chicken cool slightly and chop into 1-inch pieces.
(You can also skip this step and use rotisserie chicken.)
Preheat oven to 350°F and prepare a 13×9-inch dish with cooking spray.
Place the broccoli in the bottom of the prepared dish. Top with the chopped chicken.