In a mixing bowl, combine the mashed black beans, cooked quinoa, breadcrumbs, diced onion, grated carrot, corn kernels, and minced garlic. Mix well to combine.
Add soy sauce, chili powder, cumin, salt, and pepper. Stir until all ingredients are evenly incorporated.
Divide the mixture into 4 equal portions and shape each portion into a patty.
Heat a skillet or grill over medium heat. Lightly oil the surface to prevent sticking.
Cook the patties for about 5-7 minutes on each side, or until they are heated through and crispy on the outside.
Serve the patties on whole grain buns with your choice of toppings such as lettuce, tomato, avocado, or cheese.
For serving, consider pairing the veggie burgers with a side salad or sweet potato fries for a complete meal.
If you have leftovers, store the patties in an airtight container and freeze them for up to 3 months.