Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.
In a large bowl, combine the shredded chicken, frozen peas, frozen carrots, cream of chicken soup, milk, chopped onion, salt, and pepper. Stir until well combined.
Pour the chicken mixture into the prepared baking dish.
Separate the biscuits and place them on top of the chicken mixture, spacing them out slightly.
Bake for 30-35 minutes, or until the casserole is bubbly and the biscuits are golden brown and cooked through.
Let stand for a few minutes before serving.
Notes
This casserole is perfect for a quick weeknight dinner. You can also add other vegetables like corn or celery if desired.