He must store a large quantity of grain instead of consuming all his grain immediately.

【翻译】他必须储存大量的粮食，而不要马上把所有的粮食都吃光。

从前后文的关系来看，instead of 引导的介词短语，作“对比状语；反衬状语”。又如：

Instead of pressing forward, they drew back. 

他们不仅没有前进，反而后退了。

Plastic is sometimes used instead of leather. 

塑胶有时可以替代皮革。