Preheat the oven to 425, then spray a 9 X 13-inch baking dish with non-stick spray and set aside.
Lay the chicken on a cutting board, and using a chef knife, cut between the chicken breasts and through the bones to separate them. This allows the chicken to be laid flat to cook quicker.
Using your fingers, lift the skin off of the meat and then spread the seasoning under the skin.
Sprinkle seasoning on the skin of the chicken also.
Cook at 425 degrees until the temperature reaches 165 degrees, this can be between 30-60 minutes. Check the temperature with a thermometer until it has reached 165 degrees.
Then rinse the potatoes in a sink colander and using a cutting board, cut the potatoes in half and then quarter them.
Lay the cut potatoes on a large baking sheet that has been sprayed with non-stick spray.
Rinse the broccoli in a sink colander and cut the stems off of the broccoli crowns and then cut them into smaller pieces.
Arrange the broccoli pieces around the potatoes on the sheet-pan.
Drizzle oil over the potatoes and broccoli and then season with salt, pepper and garlic powder.
For extra flavor, carefully spoon out chicken drippings from the baking dish onto the vegetables while they are still baking.
Bake the vegetables on the sheet-pan until a knife can be inserted into the potatoes easily.
When done, remove the sheet-pan from the oven.
When the internal temperature reaches 165 degrees on the chicken, remove it from the oven and let it rest 5-7 minutes.
Finally, slice the chicken and serve with potatoes and broccoli!