If using frozen spinach, place in strainer and drain well.
Heat oil and butter in large, heavy skillet. Add ground beef and cook, stirring, until browned and crumbly. Add onion and cook until tender but not browned. Stir in basil, marjoram, oregano, salt and pepper. Stir in drained spinach and cook until liquid in spinach has evaporated. Beat eggs, add to meat mixture and cook, stirring, until eggs are set.