In a bowl, mix together the seasonings, olive oil, lime juice, garlic, cilantro, and jalapeno. Place the steak in a bag, add the marinade, mix well and refrigerate while it marinates for 1-12 hours.
Slice the peppers and onions into thin strips. Add ½ cup of olive oil to a pan and place over high heat. Add the vegetables and optionally season with more of the fajita seasonings. Cook for 5 minutes and optionally add minced garlic.
Grill the skirt steak over high heat for 3-4 minutes for each side, until it reaches your desired doneness. Let rest for 5-10 minutes.
Slice the skirt steak against the grain and serve with the vegetables.