According to Osprey New Vanguard # 37, Siker1, StuG IVs were normally issued as single companies of 14 (later 10) vehicles each to infantry, Jaeger, mountain and Volksgrenadier divisions. But there were exceptions; Panzer Abteilung 190 of the 90th Panzergrenadier Division in Italy was fully equipped with StuG IVs, as was Panzer Abt. 8 of the 20th Panzergrenadier Division, and the divisional tank battalions of the 4th and 17th SS Panzergrenadier Divisions.
It was also issued to the 5th SS Panzer Division Wiking, but the above mentioned book isn't clear about whether these StuGs were issued to the tank regiment, or to the divisional tank-destroyer battalion. Perhaps someone else can answer that.
Hope this has been useful to you.