Preheat oven to 220°C/425°F and spray an oven dish with olive oil, making sure to spray the sides and edges.
Prepare vegetables by slicing cherry tomatoes in halves, red onion into small cubes, olives in halves, and roughly chop the spinach
Crack all the eggs into a large bowl and whisk until well combined.
Add the olives and crumble in ¾ of the feta cheese.
On medium heat, sauté the onion in a pan with olive oil.
Once translucent, add cherry tomatoes and season with oregano. Once they have a nice sear, add the spinach and cook together for 1 minute.
Remove from the heat and add to the bowl with the remaining ingredients
With a spoon, mix together quickly so the eggs don’t scramble and start to cook.
Pour mixture into the greased oven dish ensuring its level and evenly spread.
Crumble over the remaining feta cheese then place in the oven to cook for 22-25 minutes. Check that it is cooked all the way through by sticking a toothpick in to make sure it comes out clean.
Remove from the oven and allow it to cool down and set for at least 10 minutes. Once rested, slice and enjoy for brunch, lunch or any time of the day!