Whether or not a four old month baby is capable of having food other than breast-fed milk or baby formula, depends on the health condition of the baby.
If the baby has not experienced any stomach related problems up till four months, he can start having solid food in his diet.
Generally, smashed food is fed to the baby, as he can swallow it without chewing. Pastes and liquid food can be included in the baby food diet. However, it is advised that nothing spicy or oily should be tried.