Export the content from multiple 'Get-ADComputer' commands - powershell

Question

Using the Get-ADComputer command I am gathering the count of the operating systems for each OU based on when the password was last set. The problem I am facing, is exporting the whole thing into a CSV file.
When I append the (Export-Csv -Path 'c:\blah') it will only take the last command and leave the others in the console.
$ou1 = 'OU=Computers,OU=Name1,DC=domain,DC=com'
$ou2 = 'OU=Computers,OU=Name2,DC=domain,DC=com'
$ou3 = 'OU=Computers,OU=name3,DC=domain,DC=com'
$prop = 'OperatingSystem -Like "Windows 10*"'
Get-ADComputer -SearchBase $ou1 -Filter $prop -Property DistinguishedName, OperatingSystem, pwdLastSet |
Select-Object DistinguishedName, OperatingSystem,
#{Name="pwdLastSet";Expression={[datetime]::FromFileTime($_.pwdLastSet)}},
#{Name="90_Days_Old";Expression={([datetime]::FromFileTime($_.pwdLastSet)).AddDays(90) -le (Get-Date)}}
Get-ADComputer -SearchBase $ou2 -Filter $prop -Property DistinguishedName, OperatingSystem, pwdLastSet |
Select-Object DistinguishedName, OperatingSystem,
#{Name="pwdLastSet";Expression={[datetime]::FromFileTime($_.pwdLastSet)}},
#{Name="90_Days_Old";Expression={([datetime]::FromFileTime($_.pwdLastSet)).AddDays(90) -le (Get-Date)}}
Get-ADComputer -SearchBase $ou3 -Filter $prop -Property DistinguishedName, OperatingSystem, pwdLastSet |
Select-Object DistinguishedName, OperatingSystem,
#{Name="pwdLastSet";Expression={[datetime]::FromFileTime($_.pwdLastSet)}},
#{Name="90_Days_Old";Expression={([datetime]::FromFileTime($_.pwdLastSet)).AddDays(90) -le (Get-Date)}}
My expected result is to have the content of all three commands into a CSV file.

Answer 1

You have a lot of redundant code. Use a loop to avoid that. Also, there's no need to convert the property pwdLastSet (which contains the raw value from the AD attribute) to a DateTime value. The Get-ADComputer cmdlet already does that for you (the name of the property you want is PasswordLastSet).
$ou = 'OU=Computers,OU=Name1,DC=domain,DC=com',
'OU=Computers,OU=Name2,DC=domain,DC=com',
'OU=Computers,OU=name3,DC=domain,DC=com'
$prop = 'OperatingSystem -like "Windows 10*"'
$ou | ForEach-Object {
Get-ADComputer -SearchBase $_ -Filter $prop -Property DistinguishedName, OperatingSystem, PasswordLastSet |
Select-Object DistinguishedName, OperatingSystem, PasswordLastSet,
#{Name="90_Days_Old";Expression={$_.PasswordLastSet.AddDays(90) -le (Get-Date)}}
} | Export-Csv 'C:\path\to\output.csv' -NoType

Answer 2

You can put all your OUs into an array then use a foreach (%) as the SearchBase. This will also allow you to pipe (|) the results to a csv:
#OUs
$OUs = #('OU=Computers,OU=Name1,DC=domain,DC=com','OU=Computers,OU=Name2,DC=domain,DC=com','OU=Computers,OU=name3,DC=domain,DC=com')
$prop = 'OperatingSystem -like "Windows 10*"'
#forach --> | CSV
$OUs | %{Get-ADComputer -Filter $prop -Properties DistinguishedName, OperatingSystem, pwdLastSet -SearchBase $_ | Select-Object DistinguishedName, OperatingSystem,
#{Name="pwdLastSet";Expression={[datetime]::FromFileTime($_.pwdLastSet)}},
#{Name="90_Days_Old";Expression={([datetime]::FromFileTime($_.pwdLastSet)).AddDays(90) -le (Get-Date)}}} | Export-Csv Test123.csv -NoTypeInformation