Heat the olive oil in a large pot over medium heat. Add the diced onion and cook for 3 minutes until it starts to soften.
Stir in the minced garlic and cook for 1 minute more, just until it becomes fragrant.
Pour in the vegetable broth. Add the drained cannellini beans, dried rosemary, salt, and black pepper.
Bring the mixture to a gentle simmer and cook for 10 minutes so the flavors blend.
Add the chopped escarole a handful at a time, stirring until it wilts into the broth. Simmer for 5 more minutes.
Taste and adjust salt or pepper if needed, then serve hot.