"Long before there was a New Testament, there was a deposit of faith concerning the nature of God, His threefold personality, His purpose in making man, the Incarnation."
This is one of the primary reasons I'm becoming Catholic!
Why Catholic and not Eastern Orthodox?
Welcome home!
Yes. It's called the Tanakh--an acronym for Torah (Teachings, or Law), Nevi'im (Prophets), and Ketuvim (Writings)--aka the Old Testament.
If the Roman Catholic Church were really the deposit of the traditions of the Apostles, it would be Torah-observant instead of making up its own rules as it went along.