Cook the bacon in a small skillet till crispy. Meanwhile, bake chicken in a 9x13" pan at 350° for 20-30 minutes or till juices run clear and internal temperature is 160°. (If you pound it thin, it will bake faster.)
Smother both sides of the chicken with BBQ sauce. Bake 3-5 more minutes.
Top with bacon and grated cheese and broil for 30-60 seconds or till cheese melts. Garnish with tomatoes and green onions.