Preheat oven to 375* degrees then prepare a baking sheet with a layer of aluminum foil and set it aside.
Cut (or shred) the prepared cooked chicken then add it to a mixing bowl with 1 ½ cups of BBQ sauce. Toss the chicken in the sauce until well covered.
Next add ½ cup of chicken to the top of each tostada shell then top the chicken with shredded cheese and place the BBQ Chicken Tostadas on the baking sheet.
Place the pan of tostadas in the warm oven and bake them at 375* degrees for 7 minutes or until the cheese has melted.
While the tostadas are in the oven dice the green onion.
Remove the tostadas from the oven then drizzle the tostadas with BBQ sauce before topping them with diced green onion. Serve immediately.