Making SharePoint JSon calls from PowerShell in SharePoint 2013

The Invoke-RestMethod in PowerShell 3 doesn’t send the appropriate header required by SharePoint 2013 to return JSon results. It took me a while to figure out this workaround.

$parameter = "my search text"
$encParam = [System.Web.HttpUtility]::UrlEncode("'$parameter'")  
$url = "http://mysp2013site/_api/search/query?querytext=$encParam"  
$wc = new-object System.Net.WebClient  
$wc.UseDefaultCredentials = $true  
$wc.Headers.Add("Accept", "application/json; odata=verbose")  
$res = $wc.DownloadString($url)  
$res