HaRav Avigdor Miller and HaRav Shlomo Wolbe both point out that the Siddur is one of the oldest sources of Written and Oral Torah. Most of what we say was formulated by the 120 Men of the Great Assembly (Anshei K’neses HaG’dolah), which was comprised of the last of the Prophets and the earliest of the Tana’im. Most of P’sukei D’Zimrah is from T’hilim, compiled by David HaMelech. Therefore, it is Torah study of the highest order. HaRav Avigdor Miller (Praise, My Soul!) writes: