Finely chop bell pepper, green onions and oyster mushrooms (if using).
Combine dried parsley, onion and garlic replacers, salt, pepper and breadcrumbs.
Whisk egg.
Put ground chicken, dry mixture, chopped veggie and whisked egg into a bowl and mix to combine. Form meatballs into 1 1/2" sized balls.
Cover cookie sheet with foil and space meatballs evenly on the foil. Carefully place the cookie sheet in the oven and cook until meatball internal temperature is 165℉, approximately 20 minutes.
If you have a mini-muffin pan, I highly recommend as it can shave about eight minutes off of the cooking time. Before you place the meatballs in the cookie sheet, make sure you do a quick, thin coat of a low-Fodmap fat to grease the mini-muffin pan to ensure easy removal later.
If you want a crisper, cooked look to the meatballs, five minutes into cooking coat with a thin layer of olive oil and put back in the oven. Flip the meatballs four minutes later and coat with another thin layer of olive oil and place back in the oven. You can broil for a minute or two if desired, but keep an eye on the internal temperature of the meatballs.