In a medium resealable plastic bag, combine the flour, garlic powder, salt, and pepper. Add the beef and shake the bag until all the cubes are coated. Refrigerate for at least 15 minutes.
Set a large nonstick soup pot over medium-high heat until it is hot enough for a spritz of water to sizzle on it. Add the oil. Add the reserved beef cubes to the pot in a single layer. Cook for about 1 minute per side, or until browned. Reduce the heat to medium. Add the mushrooms, onion, garlic, and thyme. Cook for about 10 minutes or until the onion is tender, stirring occasionally with a wooden spoon and scraping any browned bits from the pan bottom.
Add the broth and carrots. Increase the heat to high. When the broth comes to a boil, reduce the heat to low so the mixture simmers gently. Cover and cook for 45 minutes.
Add the potatoes. Cook for another 45 minutes, or until the beef is fork tender. Season with additional salt and pepper. Serve your beef stew immediately.