Brown Italian sausage over medium heat and drain, if necessary.
Remove from heat and stir in pizza sauce.
In a greased 9" x 13" baking dish, tear biscuits into quarters and place in a single layer.
Bake for 5 minutes.
Top biscuits with sausage mixture, spreading into an even layer.
Add layers of onion, green pepper, mushrooms and pepperoni.
Bake for 20 minutes.
Sprinkle mozzarella cheese over bubble pizza.
Bake for an additional 5-10 minutes or until cheese is melty and beginning to brown.
Let stand for 5-10 minutes before serving.
Notes
Feel free to substitute your favorite ingredients - beef for Italian sausage, Canadian bacon for pepperoni, different vegetables - the possibilities are endless!