This historical and pivotal sermon series began on December 1, 1523. It evidently ran right up through Christmas Eve.
2023 would be a great time to have a Bible study on 1John, with Oecolampadius' sermon series to guide you.
Here is a playlist of 17 videos consisting of a 30-min Introduction and sixteen short summaries by Oecolampadius' leading biographer, Ernst Staehelin (a contemporary colleague of Karl Barth); the summaries are newly translated and read as introductions to Bible Study sessions.
Meanwhile, as further evidence of just how groundbreaking this series was, check out this link; notice whose name appears first and notice the categories:
Tradition = Reformed and Genre = Sermon / Sort = Date (Oldest)
The title in question is the third on the list. The first is Oecolampadius' translation of a patristic sermon, the second is a collection of three sermons from 1521, which merit translation, but do not quite represent the full breakthrough to the Reformation, as they were produced while he was still in the monastery.
For the hardcover version of the Sermons on the First Epistle of John, and also for additional translations of related material, ... these Works of Oecolampadius are appearing at Barnes & Noble.