About 30 minutes before grilling, remove the steaks from the refrigerator. Allow them to sit covered at room temperature.
Chimichurri Sauce
Combine hot water, oregano, and salt in a small bowl. Let stand 5 minutes to soften oregano.
Pulse parsley, cilantro, garlic, and red pepper flakes in food processor until coarsely chopped, about ten 1-second pulses.
Add oregano water mixture and vinegar and pulse briefly to combine.
Transfer mixture to a medium-sized bowl and slowly whisk in oil until incorporated and the mixture is emulsified.
Cover with plastic wrap and let stand at room temperature for at least 30 minutes. If preparing sauce in advance, refrigerate and bring to room temperature before using.
Grilling Steak
Heat grill to medium-high heat. Clean and then carefully brush the grill grates with oil.
Brush the steaks on both sides with olive oil and season generously with salt and pepper.
Place the steaks on the grill and cook until charred grill marks appear, about 6 minutes covered.
Turn the steaks over and continue to grill until the second side is slightly charred and thermometer inserted into the center registers 115°F for rare (about 2 minutes), or 120°F for medium-rare (about 3-5 minutes), or longer for medium and medium well doneness.
Transfer steaks to a large plate and let rest, loosely tented with foil, for 10 min. Slice, serve and top with chimichurri sauce.