To be clear, this is not something that just happened during or 'after' Ataturk. The secularization (and growing ethnic nationalism) of the Ottoman/Turkish central government dates back to at the very least the beginning of the 19th century. All attempts to disentangle power from the hands of the religious authorities (the ulema) and their supporters could be seen as a part of this secularizing tradition.

The crown jewel of this whole process can be considered the Tanzimat, a series of huge reforms intended to modernize the state, its legal and social structures, as well as its military, while also maintaining imperial unity in the face of growing nationalist fractures. The Tanzimat culminated in the adoption of an actual constitution for the Ottoman Empire- unfortunately for democracy-minded reformers, the accession of Abdülhamid II ended this experiment in favor of a more autocratic style of rule.

A critical reform to consider with regards to your question is the 1856 Rescript of Reform, which in extremely clear language ended many forms of religious discrimination, allowing for non-Muslim public servants, and ending the jizya, or tax on non-Muslims (although implementing a similar system involving military service).

The secularization of the Ottoman Empire is something that all citizens were aware of, and its intensity is such that we can find some real gems from embittered contemporaries. In the Greek patriarchate, those used to the established religious pecking order prior to 1856 lamented that "The state has made us equal with the Jews. We were satisfied with Muslim superiority."

The primary source for this post was M. Şükrü Hanioğlu's A Brief History of the Late Ottoman Empire.

I think you need to be very specific when you're talking about this period. Sure, Kemalist Turkey was avowedly secular (as in separating religion and politics). They abolished religious courts, secularised family law and removed references to Islam from the constitution (See Zurcher - Turkey: A Modern History and Kili - Kemalism).

However, I don't think you could argue that the Kemalist government was anti-religious (with the exception of their opposition to Sufism). Indeed there was a big effort to use Sunni Islam as a basis for a new sort of Turkish identity. It was the Kemalists who established the Presidency of Religious Affairs (Diyanet) which funded Trukish translations of the Qur'an and hadith (Baskan - From Religious Empires to Secular States p 59). It was also the Kemalists who adopted 'millet' (which had meant a religious minority group under Ottoman rule) as the word for 'nation' and 'mehmetcik' (soldiers of Mohammad) for the army (Yavuz - 'Cleansing Islam from the Public Sphere' and 'Islamic Political Identity in Turkey').

I realise that may not be quite what you're after, but I'm afraid I can't offer much detail on pre-Kemalist Turkey.

While my knowledge of the Turkish state and the development of secularism is largely limited to the post-Young Turk coup, I will do my best to answer this, as I studied Turkey a fair bit as part of my dissertation.

The secularisation movement had been building for a while prior to Ataturk, as Koliano states in his earlier post. However, it had come in drips and drabs, as a number of the reformers saw secularisation as a means for increasing the power of the state, rather than the long-term social development it had been in Western Europe. As a consequence, the reformers could just as easily switch back to using Islam as a political tool if it was more convenient for them.

The Young Turks of the Committee of Union and Progress (CUP) exemplified this. While they generally pursued a policy of secularisation and constitutionalism, they also were willing to use Islam as a facet of their drive towards rejuvenating the Ottoman Empire, leading to things such as Pan-Turanism (the uniting of Turkic peoples under the Ottoman banner), the 'Army of Islam' led by Enver Pasha at the end of WWI which attempted to accomplish the aforementioned Pan-turanism, the call of Sultan Mehmed V for Muslims to pursue Jihad against the Allies in WWI and the attempted genocide of the Armenians and other Christians within the Empire.

Mustafa Kemal 'Ataturk' and the Kemalists of the Republican People's Party (RPP) established Turkey's independence in the aftermath of WWI and ruled it for the over 2 decades. They dropped the Islamist tendencies of the CUP and went all out on secularising Turkish society (the last Caliph was removed in 1922 by the RPP). But make no mistake here, contrary to what Kemalists will tell you, Ataturk ruled Turkey as a dictator of a one-party state. As a consequence, secularisation was overwhelmingly imposed from the top-down and was massively unpopular. This was for a couple of reasons. Firstly, Islam really formed the basis for popular cultural identity and societal cohesion outside of the major cities (where the RPP's power base was located) in the countryside, so when this was removed it was understandably viewed unfavorably. The second point is tied in with the first, which is that the RPP attempted to replace Islam with Kemalism as the unifying ideology for society...and failed miserably, as the government was not well-liked by the rural populace. This means that secularism can possess underlying authoritarian themes in Turkish politics.

What this means is that Turkey hasn't really properly become secularist- after all, the present government is Islamist- and remains deeply divided over the issue, as was seen in the unrest in 2013.

TL;DR: While the Turkish government is at least partly secularised, Turkish society as a whole can hardly be considered a 'bedrock' of secularism, largely due to clumsy attempts to implement it in the past.

Sources: Turkey: A Modern History, Erik Zurcher.

I don't have any more to hand right now, but I can find their names if necessary.