Cheesesteak Nachos

vegetable or canola oil (divided)

cubed (leftover, fully cooked beef)

onion (peeled, trimmed of the root and blossom ends, and diced)

green pepper (stem and seeds removed, and diced)

garlic clove (peeled and minced or pressed through a garlic press)

bag tortilla chips

to 4 cups shredded cheeses (See Cook's Notes)

barbecue sauce for serving