Preheat your oven to 400 degrees.
Lightly brush both sides of the tortillas with olive oil and place on a baking sheet. Lightly spinkle to top side with salt if desired. Baked at 400 degrees for 4-5 minutes per side, until crispy. Turn oven down to 350 degrees.
In a bowl, combine the chicken and 1 cup of the bbq sauce together.
Divide the chicken between the tostada shells and top each with 1/4 cup of cheese.
Bake for 6 to 8 minutes, just until the cheese is melted.
Remove from the oven and drizzle with the remaining ½ cup barbecue sauce. Sprinkle with green onions. MAkes 8 servings.