Heat oil in a small skillet over medium heat.
Add onion and sauté until translucent, about 3 minutes.
Add the broccoli to the onions; continue to sauté, stirring often, for an additional 5 - 7 minutes, until broccoli is soft but not mushy.
Transfer onion and broccoli to a large bowl and add ricotta cheese, cheddar cheese, egg, egg whites, mustard and oregano; salt and pepper to taste.