This might work a bit faster
DECLARE @ProcName sysname ,
@usercredentials sysname
set @procname=''
set @usercredentials='Development'
WHILE @procname is not null
begin
SELECT @procname = min(name)
FROM sysobjects
WHERE xtype='P' and name > @procname and name not like 'dt_%'
IF @procname is not null
BEGIN
EXEC('GRANT EXECUTE ON ' + @procname+ ' TO ' + @usercredentials)
PRINT 'Execute permissions granted on '+ @procname+ ' TO ' + @usercredentials
END
END