会议被推迟到明天早上10点开始.
至于你的补充,回答如下：先来看下牛津高阶词典中对Delay的释义：
delay
v
[I,In/pr,Tn] (cause sb to) be slow or late 使（某人）慢或迟到; 耽搁; 延误:Don't delay!Book your holiday today!别拖延!今天就定下你休假的日子!* She delayed (for) two hours and missed the train.她耽搁两个小时,把火车误了.* I was delayed by the traffic.因交通阻塞,我迟到了.
[Tn,Tg] put (sth) off until later; postpone 推迟（某事）; 延期:We must delay our journey until the weather improves.我们必须把旅行推迟,等天气好转再说.* Why have they delayed opening the school?他们为什麽延期开学?
你所提问的句子中delay是被动态,所以就是及物动词,因此释义可参照以上第二条.
再者,如果会议是一直开到明早十点的话,那这个句子就不应该用delay,而是应该用last,表示持续动作：The meeting will be lasted till ten o'clock tomorrow morning.