Slice steak into thin strips. Place steak strips, chilies, garlic, beef broth, and 1 Tbsp. fajita seasoning in a large plastic Ziploc bag. Press all the air out and let marinade for at least 1 hour. Heat vegetable oil in large skillet.
Drain some of the marinade (you don't need to drain it all out, you still want most of the chilies in with the steak) and add steak to skillet. Stir-fry until brown and cooked through. Stir in remaining fajita mix. Add onion and peppers. Prepare Spanish rice according to package directions. Add beans and stir together with rice until hot. Prepare bowls by placing a tortilla inside of the bowl. Add rice/bean mixture to bowl. Add steak and peppers/onions. Top with sliced avocado and/or cheese.