Add the oil to a large pot or Dutch oven and heat at a medium setting
Measure the flour, salt, and pepper into a medium sized bowl, and stir to combine.
Dredge the stewing beef cubes in the flour mixture. Add to the pot, and stir to thoroughly brown on all sides.
When the meat has browned, add the red onions and garlic, and sauté with the beef for about 3 minutes until the onions are softened.
Add the lemons juice and zest, oregano, and white wine to the pot and allow it to come to a simmer for about 2 minutes, until the wine has reduced somewhat.
Add the beef broth to cover the meat and stir to combine.
Lower heat to medium-low setting, and simmer, covered for at least 1 1/2 hours, until the meat is very tender. Different cuts of meat may require more time.
Garnish with fresh thyme just before serving.