A 4-month-old cannot drink milk, other than breast milk. According to Kids Health, cow milk should not be introduced until a child reaches the age of one. Family Education suggests infants at this age should be nursing on breast milk or infant formula for about 20 minutes, including burping. Formula fed babies generally take 10 to 15 minutes to complete a bottle.
In ounces, the University of California Cooperative Extension indicates the average 4-month-old should have four to five feedings a day. Generally each serving is six to seven ounces with a total of about 680 to 992gr daily.
Many babies start solid foods such as rice cereal, fruits, and vegetables at 4 months old. Once solids are introduced, babies may start drinking less. However, Kids Health points out that food at this age is a supplement; formula or breast milk will still be the child's main source of nutrition.