PREHEAT the oven to 400°F. Line a large-rimmed baking sheet with foil.
ADD peppers and onion to the baking sheet. Drizzle with 2 tablespoons of oil and toss. Sprinkle with 1/2 tablespoon taco or fajita seasoning and toss again.
MOVE peppers and onions to the outer rim of the roasting pan, creating a space in the center for the steak. Cooking the steak in the middle of the sheet pan will help it from overcooking. Place steak in the center of the sheet pan.
TOSS steak with remaining 2 tablespoons of oil. Then sprinkle with remaining 2 tablespoons of seasoning and toss again. Double check steak and veggies are in as much of a single layer as possible (pan will be full). Squeeze half a lime worth of lime juice over the steak.
BAKE at 400°F for 10 minutes. Stir the steak, especially any areas that are overlapping.
BROIL on high for 5-10 minutes, checking regularly for desired doneness of the steak. The broil adds a nice little bit of char to the steak and helps the veggies finish getting tender.
REMOVE from the oven and drain any juices from the pan. Serve with desired toppings and enjoy!