Heat olive oil in a pan over medium-high heat. Add onions and mushrooms and cook until the mushrooms are tender. Add in garlic and oregano and cook for 30 seconds. Transfer to a bowl and set aside.
To the pan, add orzo pasta, veggie stock, half and half, stir to combine.
Lower the heat to medium and let the mixture lightly simmer until the pasta is cooked al dente, about 10-15 minutes. You don’t want to mixture to boil rapidly as it will scorch the dairy.
If the pasta is not fully cooked and the mixture is low on liquid add a little more chicken stock to help cook the pasta.
Once cooked, remove the pan from the heat and stir in parmesan cheese, mushroom and onion mixture, frozen peas and salt & pepper to taste.