Chop tomato, red onion, cilantro, oregano and red bell pepper. Slice avocado into small chunks.
Place black beans, tomato, cilantro, oregano, red onion, pepper and avocado in a bowl. Season with salt and pepper. Pour lemon juice on top, and toss to combine evenly.
Place mixture in a 6x9 or other small baking dish. Crumble the queso fresco cheese evenly on top. Bake in the oven until cheese is melted, around 10 minutes.