In a large bowl, mash the black beans with a fork or potato masher until they are mostly broken down.
Add the cooked quinoa, cooked brown rice, rolled oats, breadcrumbs, ground flaxseed, garlic powder, onion powder, smoked paprika, salt, and black pepper. Mix well until fully combined.
Divide the mixture into 6-8 equal portions and shape them into thin patties, about ½ inch thick.
Heat a large non-stick skillet or griddle over medium-high heat. Working in batches if necessary, cook the patties for 3-4 minutes per side, or until they are golden brown and crispy.
Serve the veggie smash burgers on buns with your desired toppings.
