Brown the beef with the onion and garlic in a large, nonstick skillet over medium high heat for about 5 minutes. Drain.
Add the Greek seasoning and lemon juice, stirring well.
In a separate pot, bring the beef broth to a boil. Add the couscous and cook according to the package directions.
Combine the beef and the couscous. Stir well.
Arrange lettuce on a platter and top with the beef, cherry tomatoes, green onions, pepper, radishes, cucumber, parsley, and basil. If desired, drizzle with balsamic vinegar and olive oil and top with feta cheese.