In oogenesis, completion of meiosis I results in the formation of 

Primary oocyte within the tertiary follicle grows in size and completes its first meiotic division. 

It is an unequal division resulting in the formation of a large haploid secondary oocyte and a tiny first polar body. 

The secondary oocyte retains bulk of the cytoplasm (nutrient rich) of  the primary oocyte.