Heat olive oil in the bottom of a removable crock pot insert. Or in the bottom of a soup pot if you aren't using a slow cooker. Add in onions and sauté for about 5 minutes. Add in garlic and sauté another 1-2 minutes or until fragrant.
Add in the stock, rosemary, beans, lentils, salt and pepper. Bring to boil and then shut off and place in crock pot. Set crock pot on medium and cook for about 6-8 hours. If not using a crock pot, turn soup down to low and cover. Cook on low for about 60 minutes.
Remove rosemary springs, leaving the leaves int the soup. Add in the spinach and parsley to the soup and blend. Taste and adjust for seasonings. Serve hot!