01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - Heat olive oil in a skillet over medium heat. Add onion and cook for 3-4 minutes until translucent.
03 - Add garlic and red bell pepper to the skillet; cook for 2-3 minutes until softened.
04 - Stir in chopped spinach and cook until wilted, about 2 minutes. Remove from heat and let cool slightly.
05 - In a bowl, mix the cooked vegetables with feta, cheddar, oregano, salt, and black pepper until evenly combined.
06 - Roll out the puff pastry and cut into six equal rectangles.
07 - Place a generous spoonful of filling onto one half of each rectangle, leaving a border around the edges.
08 - Fold the pastry over the filling to form parcels and press edges firmly with a fork to seal.
09 - Transfer pastries to the prepared baking sheet and brush the tops with beaten egg.
10 - Bake for 18-22 minutes until golden brown and puffed.
11 - Remove from oven and allow pastries to cool slightly before serving.