In a large cast iron or non-stick skillet, heat 2 tbsp of olive oil over medium heat. Add in the diced onions, and cook until translucent and soft, about 5-6 minutes.
Place the cooked onions in the food processor with half of the black beans. Blend on high until a paste has formed. Add in the gluten, nutritional yeast, tomato paste, Worcestershire sauce, soy sauce, thyme, oregano and black pepper. Blend for a few minutes until blend and to work the gluten. A ball may form - stop the machine occasionally and break it up. Leave the mixture in the food processor to rest while you cook the mushrooms.
Return the skillet to the stove and add in 3 tbsp of olive oil over medium-high heat. Add in the diced mushrooms, and cook until browned and they're no longer releasing any liquid. This should take 8-10 minutes.
Add the mushrooms and the rest of the black beans to the food processor and pulse a few times to blend the mushrooms and beans in. Don't over process - you want pieces of mushrooms and beans intact for texture.
Place the mixture in a large bowl, and add the veggie ground. Mix well with a spatula or your hands. Knead/squeeze the mixture for 2 minutes to work the gluten. Using a large muffin scoop or a 1/2 cup measure sprayed with oil to scoop the mixture, form the mixture into 8 patties and place on large baking sheet. Cover with plastic wrap and place in the fridge for about an hour.
When ready to grill, heat the barbecue to medium-high and brush the grill with oil. Brush the patties with oil, place them on the hot grill and close the lid. Cook for 4 to 5 minutes or until you have dark grill marks, then gently flip. Cook for another 3 to 4 minutes, brushing with barbecue sauce if desired.
Remove burgers from grill, and place on a clean baking sheet. They will firm up even more as they cool slightly. Toast the burger buns. Serve with your favorite burger toppings and condiments.