Combine all ingredients (except vinegar and oil) in a food processor and pulse until roughly chopped. Add vinegar and oil and pulse until combined. Thin with a little water, if necessary. Transfer to a bowl, cover, and refrigerate. Serve at room temperature. Can be made 1 day ahead.
For the Steak:
Use a pan, grill pan, or grill. Good cuts for Chimichurri Sauce: Skirt Steak, Flank Steak, Tri-Tip, Beef Flanken Style Short Ribs, Beef Tenderloin
*Thanks to Chef Linda Martin of Scottsdale, Arizona for this GREAT recipe!