Heat the olive oil in a large pot over medium heat. Add the onion and cook until it softens, about 4 minutes. Stir in the garlic and cook for 1 minute more.
Sprinkle in the dried oregano and cumin. Stir for 30 seconds so the spices coat the onion and release their scent.
Add the rinsed lentils, diced tomatoes, and vegetable broth. Bring the mixture to a boil, then reduce to a simmer. Cover and cook for 20 minutes.
Stir in the diced bell peppers. Continue simmering uncovered for 10 minutes so the peppers soften but keep some texture.
Add the sweet corn kernels and cook for 5 more minutes until the corn is heated through and the lentils are tender.
Season with salt and black pepper to taste. Serve hot with lime wedges on the side.