Make marinade: Pour oil, lime juice, soy sauce, garlic, chili powder, cumin and oregano into a large container. Whisk to combine everything together.
Marinate steak: Place steak into the marinade mixture; toss to coat the steak in the marinade. Cover bowl and place in refrigerator. Let steak marinade for 30 minutes or up to 12 hours. While the steak is marinating, make salsa, guac, and taco toppings.
Make salsa: Prep salsa ingredients per instruction above. Place all the ingredients (except the tortilla chips) in a food processor or blender and pulse until smooth. Season with salt and pepper to taste. Reserve in the fridge until you are ready to serve.
Make guacamole: Mash the avocado with a fork until it is smooth. Add the remaining ingredients and stir. Season with salt and pepper to taste. Add more lime juice to taste if desired.
Heat a grill or griddle pan on medium heat.
Prep cilantro, red onion, and lime for tacos per instruction above.
Cook steak: Grill the steak on both sides until it reaches your desired temperature (see below). Set the steak aside to rest for 5 minutes before slicing thin against the grain.
Lightly grill the tortilla shells on each side to warm.
Serve: Stuff the steak (about 6 oz per portion) into warmed tortillas and top with cilantro, red onion, guacamole, and lime juice. Enjoy with chips and salsa and beer.