I wish to alter the permissions for the tables inside a SQL-Server database at the same time. It is possible to method of doing this?

Run the outcomes of the script (change to match your needs):

SELECT
    'GRANT SELECT ON ' + OBJECT_NAME(o.object_id) + ' TO myRole'
FROM
    sys.objects o
WHERE
    OBJECTPROPERTY(o.object_id, 'IsMSSHipped') = 0
    AND
    OBJECTPROPERTY(o.object_id, 'IsTable') = 1
ORDER BY
    OBJECT_NAME(o.object_id)

Provided all your tables fit in with exactly the same schema, you can modify permissions in the Schema level.

See Grant Schema Permissions

You are able to write a script that retrieves the group of tables after which grants or loans/declines permissions through dynamic SQL.

However, I believe a much better approach is always to produce a role, grant privileges to that particular role, after which add/remove people from that role when needed.