Heat a frying pan over medium-low heat. Saute chopped onion until translucent and fragrant. Remove from heat.
Add onions, black beans, quinoa, salt and oregano to a food processor. Pulse to combine. If necessary, add some water or aquafaba (bean water) 1 teaspoon at a time to help process the mixture. mix until well combined.
Heat a grill or grill pan over medium-low heat.
Divide the mixture into 6-8 portions and form into patties. Dust patties with a pinch of tapioca starch, ensuring that both sides are covered.
Place on hot oiled grill over medium-low heat and cook about 6 minutes a side or until heated through.
Toast gluten-free hamburger bun and serve with your favorite allergy-friendly toppings: lettuce, ketchup, mustard, pickles, bbq sauce.
These burger patties store well in the refrigerator in an airtight container.