To change the ownership for a bunch of tables in a database from one owner to another, you can use the following script developed by David Penton (www.davidpenton.com).  Basically, you need to set the @oldOwner and @newOwner values to the values you want to use, and then it will generate the SQL needed for each change owner operation and run them all using the sp_MSforeachteable procedure that is included in SQL Server.

Bulk Table Change Owner:

DECLARE @oldOwner sysname, @newOwner sysname, @sql varchar(1000)

SELECT
  @oldOwner = 'aspalliance'
  , @newOwner = 'dbo'
  , @sql = '
  IF EXISTS (SELECT NULL FROM INFORMATION_SCHEMA.TABLES
  WHERE
      QUOTENAME(TABLE_SCHEMA)+''.''+QUOTENAME(TABLE_NAME) = ''?''
      AND TABLE_SCHEMA = ''' + @oldOwner + '''
  )
  EXECUTE sp_changeobjectowner ''?'', ''' + @newOwner + ''''

EXECUTE sp_MSforeachtable @sql