Heat the olive oil in a large pot over medium heat. Add the onion and garlic and cook for 3 minutes until the onion softens.
Add the carrots, potatoes, and fennel. Stir and cook for 5 minutes to let the vegetables begin to soften.
Stir in the lentils, oregano, thyme, rosemary, salt, and pepper. Pour in the vegetable broth and bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 25 minutes. Stir once or twice during cooking until the lentils and potatoes are tender.
Remove the lid and simmer for 5 more minutes if you prefer a thicker stew. Taste and adjust salt if needed.
Ladle into bowls and top with fresh parsley. Serve with lemon wedges on the side.