Brush a griddle pan with about 1 tsp of the oil and griddle the aubergines until nicely charred, then remove. Repeat with the courgettes and onions, using a little more oil if you need to.
Remove the tray from the oven and brush with a little oil.
Brush a large sheet of filo with oil, top with another sheet, add a little more oil and repeat with the final sheet.
Transfer the pastry to the hot tray, pushing it into the edges a little.
Arrange the griddled veg on top, then season.
Add the tomatoes, cut-side up, then drizzle on the vinegar and any remaining oil. Crumble on the feta and sprinkle with oregano. Cook for about 20 mins until crispy and golden.