Prepare lasagna noodles according to package directions. Preheat oven to 350 degrees.
Heat olive oil in a large saucepan over medium heat; add onions, mushrooms, pepper, & garlic. Saute 3-4 minutes, stirring occasionally. Add rest of ingredients, except Italian seasoning & cheese. Simmer over low heat for 10 minutes, stirring occasionally.
Lightly oil a 9 x 13 inch pan. Lay cooked noodles on bottom of pan to cover it, then add layers of half the the sauce mix & 1 1/2 cups of cheese. Sprinkle w/ Italian seasoning. Repeat layers . Bake uncovered for 25 minutes or until bubbly. (you can cover w/ aluminum foil if cheese starts to burn)