Preheat over to 375.
Boil spinach leaves for 2 minutes, then rinse in cold water and leave to drain.
Chop onion, leeks, green <g class="gr_ gr_91 gr-alert gr_gramm gr_inline_cards gr_run_anim Punctuation only-ins replaceWithoutSep" id="91" data-gr-id="91">onion</g> and cilantro.
Add eggs and oats.
Chop feta cheese and add to mix.
Add cooled spinach. Mix well.
Oil baking pan with cooking spray and avocado oil. Put mixture.
Bake for 50 minutes.
Move to top rack and bake for 10 more minutes.
Take out from oven, let cool and serve.