Can you access ODATA with PowerShell?

Yes you can. However you need to use PowerShell Version 4.0. On the computer where this post is created PowerShell 4.0 is installed by default (Windows 8.1). But if you are using Windows 7.0 read here:

http://hodentekhelp.blogspot.com/2015/03/how-do-you-install-windows-powershell.html

Here is an example.
I take the example of using the ODATA service provided by ODATA.Org
Here is the URL of this service:
http://services.odata.org/OData/Odata.Svc

If you were to type this into you browser,you would see this.

This shows meta data of the collection in this service

Launch Windows PowerShell with elevated permissions.

Verify you are using Version 4
--------
PS C:\Windows\system32> $PSversionTable.PSversion
Major  Minor  Build  Revision
-----  -----  -----  --------
4      0      -1     -1
------------

Declare a $Categories variable as shown
$categories=Invoke-RestMethod http://Services.odata.org/OData/OData.svc/Categories
You will be returned to the next line if there are no errors
Let us see what is in categories
---------
PS C:\Windows\system32> $categories
id       : http://services.odata.org/OData/OData.svc/Categories(0)
category : category
link     : {link, link, link}
title    : title
updated  : 2014-11-27T21:11:29Z
author   : author
content  : content

id       : http://services.odata.org/OData/OData.svc/Categories(1)
category : category
link     : {link, link, link}
title    : title
updated  : 2014-11-27T21:11:29Z
author   : author
content  : content

id       : http://services.odata.org/OData/OData.svc/Categories(2)
category : category
link     : {link, link, link}
title    : title
updated  : 2014-11-27T21:11:29Z
author   : author
content  : content
------------------
Looks like there are three categories
Let us look at the titles and link of these categories
-------------
PS C:\Windows\system32> $categories.title
type                                                        #text
----                                                        -----
text                                                        Food
text                                                        Beverages
text                                                        Electronics

PS C:\Windows\system32> $categories.link
rel                                     title                                   href
---                                     -----                                   ----
edit                                    Category                                Categories(0)
http://schemas.microsoft.com/ado/200... Products                                Categories(0)/Products
http://schemas.microsoft.com/ado/200... Products                                Categories(0)/$links/Products
edit                                    Category                                Categories(1)
http://schemas.microsoft.com/ado/200... Products                                Categories(1)/Products
http://schemas.microsoft.com/ado/200... Products                                Categories(1)/$links/Products
edit                                    Category                                Categories(2)
http://schemas.microsoft.com/ado/200... Products                                Categories(2)/Products
http://schemas.microsoft.com/ado/200... Products                                Categories(2)/$links/Products