As far as I know, Orthodox do not meditate on mysteries during prayer, at least not in the disciplined and structured way Roman Catholics do when praying the Rosary (the Sorrowful Mysteries, the Joyful Mysteries, etc). In fact, the entire concept of meditating on a particular subject or event in the life of Christ WHILE PRAYING is rather foreign to Orthodox thought. That doesn't mean its "bad". I think it just means that our prayer forms in the East never developed that particular custom. In fact, you see much the same thing with Stations of the Cross. To me it reminds me of the Rosary in that it is a structured mediation on the Via Dolorosa. At each station one mediates on a particular aspect of Christ's passion. As far as I know, there is NOTHING in Orthodoxy like either one of these, at least not in its meditative aspect. Some have compared the Jesus Prayer to the Rosary, but the analogy only goes so rare. While any Roman Catholic can recite the Rosary, the Orthodox Church is actually a bit RELUCTANT to encourage laymen (without proper spiritual guidance) to pray the Jesus Prayer, at least for extended periods. And when we pray the Jesus prayer we are sternly warned about not using our imagination, not seeking images, visions etc. because these will almost always be forms of demonic delusion rather than the real thing. I think the reason for this is that the Orthodox have generally viewed the imagination as a dangerous thing, and not something to be made use of in prayer.