Heat the olive oil in a 30 cm / 12-inch deep skillet over medium heat. Add the onion and cook for 4 to 5 minutes, until soft and translucent.
Add the garlic and dried oregano. Cook for 30 seconds, stirring, until fragrant.
Add the cherry tomatoes and cook for 3 to 4 minutes, until they start to soften and release their juice.
Pour in the vegetable broth and bring to a simmer. Season with the salt and black pepper.
Stir in the orzo. Reduce the heat to medium-low, cover, and simmer for 12 to 14 minutes, stirring every few minutes, until the orzo is tender and most of the liquid is absorbed.
Remove the skillet from the heat and stir in half the feta until it melts into the sauce.
Crumble the remaining feta over the top. Cover for 2 minutes to let it soften slightly.
Sprinkle with fresh basil and red pepper flakes if using. Serve warm.