In large bowl, combine beef, crumbs, egg, onion, salt and oregano. Stir in 1/2 tomato sauce; set aside.
Cut 2 pieces of waxed paper 15 inches long. Unroll crescent roll dough and don't separate. Lay end to end on top of wax paper and place second piece of wax paper on top. Now take rolling pin and roll the dough out till it's half the thickness that it was originally .
Place meat mixture in center and spread out over dough. Sprinkle meat with cheese, bell pepper & mushrooms & top with remaining tomato sauce.
Roll up meat, jelly-roll fashion, starting at narrow end; use wax paper to help.
Place seam side down in non-stick 9-1/4-in. x 5-1/2 inches x 2-3/4-in. bread pan.
Bake at 375 degrees F for 30 minutes. Drain off any fat that accumulates & then return to oven for 30 minutes.