Pat steak dry and rub with olive oil, salt, pepper, and garlic powder.
Grill steak for 4–6 minutes per side, depending on thickness and desired doneness.
While steak cooks, combine parsley, oregano, garlic, olive oil, red wine vinegar, red pepper flakes, salt, and black pepper in a bowl to make chimichurri.
Remove steak from grill and let rest for 5 minutes.
Slice steak against the grain and spoon chimichurri sauce over the top.
Serve immediately with extra chimichurri on the side.
Notes
For best results, marinate the steak with salt for 30 minutes beforehand.
Chimichurri can be made a day ahead for deeper flavor.
Use a food processor for a quicker chimichurri, but avoid over-blending.