While Luther was busy battling the papal emissaries and civil authorities in Germany, Catholic priest Ulrich Zwingli (1484-1531) started his reform movement in Zurich, Switzerland. That area being German-speaking, the people were already affected by the tide of reform from the north. Around 1519, Zwingli began to preach against indulgences, Mariolatry, clerical celibacy, and other doctrines of the Catholic Church. Though Zwingli claimed independence from Luther, he agreed with Luther in many areas and distributed Luther’s tracts throughout the  country. In contrast with the more conservative Luther, however, Zwingli advocated the removal of all vestiges of the Roman Church​—images, crucifixes, clerical garb, even liturgical music. A more serious controversy between the two Reformers, however, was on the issue of the Eucharist, or Mass (Communion). Luther, insisting on a literal interpretation of Jesus’ words, ‘This is my body,’ believed that the body and blood of Christ were miraculously present in the bread and wine served at Communion. Zwingli, on the other hand, argued, in his treatise On the Lord’s Supper, that Jesus’ statement “must be taken figuratively or metaphorically; ‘This is my body,’ means, ‘The bread signifies my body,’ or ‘is a figure of my body.’” Because of this difference, the two Reformers parted ways. Zwingli continued to preach his reform doctrines in Zurich and effected many changes there. Other cities soon followed his lead, but most people in the rural areas, being more conservative, clung to Catholicism. The conflict between the two factions became so great that civil war broke out between Swiss Protestants and Roman Catholics. Zwingli, serving as an army chaplain, was killed in the battle of Kappel, near the Lake of Zug, in 1531. When peace finally came, each district was given the right to decide its own form of religion, Protestant or Catholic. Luther and Zwingli had paved the way towards this belief with their 'faith alone' principle, and their persistent affirmation of salvation as a gift from God that cannot be earned by human effort. But neither reformer had dealt with this implicit concept of election thoroughly or systematically. Calvin, in contrast, embraced the logical conclusion of sola fide, sola gratia, and made God's overwhelming agency the very structure of his systematic theology, passing on to his disciples a firm, strident belief in election and predestination. The earliest Anabaptists—in this case, members of the group that historians have come to call the Swiss Brethren—insisted that the Bible alone was the basis for their beliefs and practices. They correctly claimed that scripture included no direct mandate for infant baptism; Zwingli defended it by analogy to the Jewish practice of circumcision. But however biblical their view, it was defined as illegal by local authorities and thereby became a 'radical' position, their insistence on believers' baptism a 'radical' practice.

'Protestatio' at Diet of Speyer gives its name to 'Protestants'; failure of Luther and Zwingli to agree over Eucharist at Colloquy of Marburg; first religious war in Switzerland