Read her lips: No big words.

The notoriously-ditzy Jessica Simpson tweaked plans to give a lengthy prepared speech at the Operation Smile Gala in Beverly Hills this month after stumbling over several “big” words once telepromoters started running during a pre-show rehearsal.

A spywitness tells Star Magazine: “She got so flustered and complained that she couldn’t even pronounce half of the words.”

Sources say Jessica ended up making up her own version of the speech, “It was shorter and much simpler.”