Drain and rinse the artichoke hearts, then pat dry. If the hearts are whole, cut into quarters lengthwise. Set aside.
In a large bowl, stir together the olive oil, lemon zest, lemon juice, parsley, salt, peppercorns, and capers with a fork. Add the artichoke hearts and turn gently to coat. Cover and let stand at room temperature for 1 hour, then cover and refrigerate for at least 24 hou