Heat the olive oil in a large skillet over medium heat.
Add the chopped bell peppers and red onion, and cook until softened, about 5 minutes.
Stir in the corn kernels, black beans, cumin, chili powder, salt, and black pepper. Cook for another 5 minutes or until everything is heated through.
Warm the corn tortillas in a separate skillet or microwave.
Assemble the tacos by placing the vegetable mixture onto each tortilla.
Top with sliced avocado, cilantro, and crumbled cheese if desired.
Serve with lime wedges on the side.