All Christians, including “non-liturgical” Christians, worship with a liturgy, in the sense of a predictable order of worship that reflects their theology. The key question is what the liturgy is and what it means. A new book is out on this subject by Yale worship scholar Melanie Ross, Evangelical versus Liturgical?: Defying a Dichotomy.
From the foreword by Mark Noll:
The result of her pioneering effort is a challenge to scholars of liturgy to recognize that “free churches,” which may be inert to traditional or formal liturgical studies, nonetheless can possess responsible (if unselfconscious) liturgical traditions. Along the way it shows that these churches have often developed insights about worship that formally trained liturgical scholars need to appreciate, and that these churches deserve a place at the table in liturgical study more generally.