Preheat oven to 375 degrees F.
Turn multi-cooker (Instant Pot) to Saute mode and coat the bottom of the liner with oil (1-2 tbsp).
When hot add sliced onions and cook for 2-3 minutes until translucent. Turn off Saute mode.
Add chicken and your favorite BBQ sauce.
Cook on High Pressure for 12 mins. Release pressure.
Shred chicken using a fork and adjust seasoning if necessary.
Layer tortilla chips, shredded BBQ chicken, and cheese on a large sheet pan/baking tray. Bake until cheese is melty (5 minutes or so) and remove from oven.
Serve with coleslaw and your favorite toppings!