Wrap tortillas securely in aluminum foil; bake at 350 degrees for 15 minutes or until thoroughly heated.
Combine tomato juice, seasoning mix and oil; stir well, and set aside.
Cook ground beef in a large skillet until browned, stirring to crumble; drain.
Stir in beans and 1/2 cup tomato juice mixture.
Bring to a boil; cover, reduce heat, and simmer 5 minutes or until mixture is thoroughly heated, stirring occasionally.
Remove from heat.
Place 1/4 cup beef mixture and 2-1/2 tbsp cheese down center of each tortilla.
Roll up tortillas, and place seam side down in a lightly greased 13x9 inch-baking dish.
Pour remaining tomato juice mixture over casserole.
Cover and bake at 350 degrees for 30 - 35 minutes.
Uncover and sprinkle with remaining cheese; bake an additional 5 minutes or until cheese melts.
Peel and cube avocado; toss with lemon juice.
Sprinkle avocado, lettuce and tomato over casserole.
Serve immediately.