Heat oven to 400° F.
Combine the chicken, vegetables, soup, salt, pepper, and 3/4 cup water in a large bowl. Transfer the mixture to an oven-safe casserole, cover with foil, and bake for 30 minutes. After 15 minutes, place the biscuits on a baking sheet and bake until the biscuits are golden brown and cooked through, about 15 minutes. Remove both the casserole and the biscuits from the oven. Uncover the casserole, place the biscuits on top, and serve.