Looking at another post I was able to get what I wanted with the following code...
Select Distinct Top 1000000 tblADusers.Username,
tblADusers.Userdomain,
Max(tblCPlogoninfo.logontime) As 'last logon'
From tblADusers
Inner Join tblADMembership On tblADMembership.ChildAdObjectID =
tblADusers.ADObjectID
Inner Join tblADGroups On tblADMembership.ParentAdObjectID =
tblADGroups.ADObjectID
Inner Join tblCPlogoninfo On tblCPlogoninfo.Username = tblADusers.Username And
tblCPlogoninfo.Domain = tblADusers.Userdomain
Group By tblADusers.Username,
tblADusers.Userdomain