Preheat your grill to medium-high heat.
In a small bowl, mix together the chili powder, cumin, paprika, minced garlic, salt, and pepper. Rub this spice blend all over the steak.
Drizzle 1 tablespoon of vegetable oil over the steaks to coat them lightly. Place the steak on the grill and cook for about 4-5 minutes on each side for medium-rare doneness. Once cooked, let the steak rest for 5 minutes.
Toss the bell pepper strips and onion wedges with the remaining 1 1/2 tablespoons of vegetable oil. Season with a pinch of salt and pepper.
Grill the vegetables, turning them occasionally, until they are charred and soft, which should take about 6-8 minutes.
Slice the steak thinly against the grain and serve it alongside the grilled peppers and onion on warmed tortillas.