Preheat oven to 350°F. Grease a 9x13 casserole dish.
Sprinkle the cut sausage in the bottom of the casserole dish.
Add the chopped tomatoes, green onions and cheddar cheese, making sure to evenly distribute them among the pan.
In a medium bowl, mix baking mix, milk, eggs, salt, pepper and oregano.
Pour over ingredients in casserole dish.
You can cover and refrigerate overnight or bake immediately in a 350 degree oven for 35-40 minutes until firm when a fork is placed in the middle.
If the top gets too dark, you can cover with foil for the remainder of the cooking time.