Lightly grease jelly roll pan, 15 1/2 x 10 1/2 x 1 inch jelly pan, or cookie sheet.
Mix baking mix and water until soft dough forms.
Gently smooth dough into ball on floured surface.
Knead 20 times.
Pat dough on bottom and up sides of pan with floured hands or roll into rectangle, 13x10 inches, and place on cookie sheet.
Pinch edges of rectangle, forming 3/4 inch rim.
Cook and stir ground beef, onion, salt and garlic until beef is brown, drain.
Mix tomato sauce and Italian seasoning, spread evenly over dough.
Spoon beef mixture evenly over sauce.
Top with mushrooms, green pepper and cheese.
Bake in preheated 425° oven for 20 minutes or until crust is golden brown.