Heat oven to 375 degrees F. Mix soup and 1/2 cup sour cream in an 8-inch square baking dish. Add chicken, vegetables and cheese; mix. Place baking mix in medium bowl. Add remaining 1/4 cup sour cream and milk; stir until stiff dough forms.
Drop by tablespoonfuls into 6 mounds over chicken mixture. Bake 35 minutes or until biscuits are golden brown and chicken mixture is hot and bubbly.