Heat the olive oil in a large saucepan. Add the onion and cook for 5 minutes until soft.
Add the garlic and oregano, cook for 1 minute until fragrant.
Pour in the vegetable stock and bring to a simmer. Add the frozen peas and cook for 5 minutes.
Stir in the cooked rice and lemon zest. Heat through for 2-3 minutes.
Remove from the heat and stir in the lemon juice and most of the chopped parsley. Season well with salt and black pepper.
Serve in warm bowls, garnished with the remaining parsley and an extra twist of black pepper.