PowerShell exposes environmental variables via the $Env: scope (you can read more about scopes here)

So to access the USERPROFILE environmental variable, you could do the following (note, I'm using Write-Host in place of echo here, see this answer for details on the difference between the two):

Write-Host $Env:USERPROFILE

PowerShell also exposes a number of automatic variables and these are made available to all scripts and commands. $HOME for example is one such automatic variable.

For further information on these, see Automatic Variables

Please specify the scope when setting the variable:

Saving environment variables with SetEnvironmentVariable

On Windows, you can specify a scope for the SetEnvironmentVariable method as the third parameter to set the environment variable in that scope. The machine and user scopes both persist outside of the current process, allowing you to save a new or changed environment variable.

[System.Environment]::SetEnvironmentVariable('ResourceGroup','AZ_Resource_Group', 'Machine')

[System.Environment]::SetEnvironmentVariable('ResourceGroup','AZ_Resource_Group', 'User')

I think you may be running up against user scope vs machine scope. I’m guessing you are setting the user scope in your command and not the machine scope.

Specify the machine scope.

about Environment Variables - PowerShell

Describes how to access and manage environment variables in PowerShell.

Thanks, Managed to get something to work… Will do some more testing but it appears to be working correctly now.

#This section are the variables for each of the environmental variables.
        $oracle_envar = ';C:\oracle'
        $odac12_envar = ';C:\oracle\odac12'
        $odac12bin_envar = ';C:\oracle\odac12\bin'
        $odac12_32bit_envar = ';C:\oracle\odac12_32bit'
        $odac12bin_32bit_envar = ';C:\oracle\odac12_32bit\bin'

        $env = Get-ChildItem Env:\Path

        if ($env -contains '*C:\oracle*')
        {
        
        }
        elseif ([System.Environment]::Is64BitProcess) 
        {
        [System.Environment]::SetEnvironmentVariable('PATH', $Env:Path + "$odac12_envar $odac12bin_envar $odac12_32bit_envar $oracle_envar $odac12bin_32bit_envar", 'Machine')
        }
        else
        {
        [System.Environment]::SetEnvironmentVariable('PATH', $Env:Path + "$odac12_32bit_envar $oracle_envar $odac12bin_32bit_envar", 'Machine')
        } 

And just because this will bug me, you can reduce the lines of code necessary with something like this:

#This section are the variables for each of the environmental variables.
        $oracle_envar = ';C:\oracle'
        $odac12_envar = ';C:\oracle\odac12'
        $odac12bin_envar = ';C:\oracle\odac12\bin'
        $odac12_32bit_envar = ';C:\oracle\odac12_32bit'
        $odac12bin_32bit_envar = ';C:\oracle\odac12_32bit\bin'

        $env = Get-ChildItem Env:\Path

        if ([System.Environment]::Is64BitProcess -and $env -notcontains '*C:\oracle*')
        {
			[System.Environment]::SetEnvironmentVariable('PATH', $Env:Path + "$odac12_envar $odac12bin_envar $odac12_32bit_envar $oracle_envar $odac12bin_32bit_envar", 'Machine')
        }
        elseif (-not [System.Environment]::Is64BitProcess -and $env -notcontains '*C:\oracle*')
        {
			[System.Environment]::SetEnvironmentVariable('PATH', $Env:Path + "$odac12_32bit_envar $oracle_envar $odac12bin_32bit_envar", 'Machine')
        }
		else
		{
			Write-Output "This machine already has the environment variable set."
		}

But then when I got done it ended up being more lines of code because I added an elseif to better determine if the 32-bit version is already set or not.