
Pulse the garlic, red onion, oregano, parsley, ½ teaspoon salt, and sugar in a food processor until roughly chopped.
Add the olive oil and vinegar, and pulse until combined but still chopped.
Transfer to a serving dish and stir in pepper flakes if desired.
Heat a grill or grill pan to medium-high. Season strip steaks with 1 teaspoon salt and ½ pepper.
Lightly oil grill.
Grill strip steaks for about 4 to 6 minutes on each side for medium. About 3 to 5 minutes per side for medium-rare.
Transfer the steak to a cutting board and let it rest for about 5 minutes.
Slice each steak across the grain and drizzle with chimichurri sauce. Serve immediately.