Hello David
The unit that introduced the type on the Eastern Front was I./JG 51 which arrived at Lyuban on 10 September 1942 with Fw 190 A-2 and A-3 fighters after re-equipping at Jesau in August 1942. However, there was little enemy aerial activity during the five weeks the Gruppe remained on the Leningrad-Volkov sector and on 17 October 1942 the Gruppe was transferred to Vyazma on the Moscow sector but here too there was little enemy aerial activity. Stab/JG 51 converted to the Fw 190 A-3 in November 1942 and III./JG 51 began conversion to the Fw 190 A-2 and A-3 that month as well but it was not until January 1943 that the Gruppe completed the conversion process from the Bf 109 F-2. IV./JG 51 began conversion to the Fw 190 A-4 in January 1943 and the process was complete by March 1943. The Stabsstaffel of JG 51 was equipped with the Fw 190 A-4 in January 1943 and was mainly used in the Jabo role. The first major actions that these units encountered occurred during Operation Mars and the operations conducted during the siege of Velikiye Luki during which I./JG 51 claimed 29 victories on 4 December 1942. Perhaps the reasons why the introduction of the type on the Eastern Front was not as noteworthy as its introduction on the Western Front was due to the relative lack of enemy aerial activity for some time following its arrival as well as the fact that the attention of both sides was focused on the events at and around Stalingrad. Andrew Arthy has a quite nice article on the conversion of JG 51 at
http://fw190.hobbyvista.com/earlyjg51190s.htm.
Horrido!
Leo