Baby food question!

Micayla Jane
When my son was 3.5mo, his pediatrician suggested that we start him on cereal due to the results of his KUB & other abdominal tests.
At the last appointment, his 4mo appointment, she gave us the okay to start him on baby food.
My question is, when am I able to take cereal out of his diet and just feed him baby food & formula?
He is 4.5mo now, and he does not enjoy cereal at all since I added baby food to his diet. (I mix his cereal with formula, not water & will not mix it with water due to lack of nutrition.)
Any suggestions? Maybe I could switch from rice cereal to oatmeal instead, since it has more flavor? TIA y'all!