To cook lamb:
Prepare grill. Cut the strings that are tying the leg together. Rub salt and pepper on both sides of the boneless leg.
The boneless leg of lamb shown grilled for 10 minutes on one side over a rather high heat, 6 minutes on the other. The best thing to do is to test with a meat thermometer unless you have a natural feel for cooking meat. Our lamb was 130 degrees when it came off the grill. Let it stand for 10 minutes. Slice thinly and plate.
In a food processor, process garlic. Add parsley and oregano and process until chopped fine. This is not a pesto so don't liquefy the herbs. Transfer to a bowl. Add olive oil, lemon juice, salt, pepper and red pepper flakes. Stir and set aside. Is best if flavors meld in the fridge. Serve as a sauce for the grilled lamb.
The Chimmichurri Sauce will keep for at least a day. Leftovers are good on any kind of vegetable or potato salad. It is a flavorful sauce with a fresh zingy taste.