Preheat grill to medium high heat. Brush flatbread with oil and lightly season with salt and pepper.
Once grill is hot, add bread and grill on each side for 2 to 3 minutes.
Remove from heat and top each with halve of the shredded cheese and bacon slices.
Place flatbread back on the grill, over medium heat, and grill for 3 to 4 minutes or until the cheese has melted and the flatbreads have crisped up.
Remove from grill and top with cherry tomatoes, shredded lettuce, avocado, and red onion, if using.
Lightly season with salt and pepper and serve.