Add the chicken, onions, red peppers, mushrooms, and peas to a large resealable plastic bag. Add in the seasonings and give it a quick shake. Remove excess air from the bag, seal and freeze.
Take the filling out of the freezer to thaw. Dump the bag contents into a skillet over medium-high heat. Cook for 5 minutes.
Add the butter and flour and stir. When well mixed in, slowly pour in the milk.
Heat for another 3-5 minutes until sauce has thickened slightly.
Transfer the chicken pot pie filling to a casserole dish.
Bake at 400° for 18-20 minutes and the biscuits are golden brown.