I used a grower feed from the time I brought them home until they were all laying. Once the first egg came, I added a dish of oyster shell to the pen for supplemental calcium. Once all of them were laying, I switched to layer feed.
If you're using a medicated starter, you can switch to grower whenever you like. Some wait until they reach laying age and go straight from chick feed to layer. Others switch to grower after a few weeks of soil exposure. It depends a great deal on feed availability and personal preference.