Preheat the oven to 400°F.
Thaw the frozen spinach and squeeze out excess water.
Roll out the puff pastry on a floured surface to a thickness of about 1/8 inch.
Mix together the spinach, feta cheese, cream cheese, garlic powder, onion powder, salt, and pepper.
Spread the spinach mixture evenly over the center of the puff pastry, leaving a 1-inch border around the edges.
Brush the edges of the puff pastry with the olive oil.
Fold the puff pastry over the filling, pressing the edges to seal.
Brush the top of the puff pastry with the beaten egg for a golden glaze.
Bake the puff pastry for 20-25 minutes, or until golden brown.
Remove from the oven and let cool for 5 minutes before serving.