2 month old and formula/cereal?

The only thing you can do is offer more ounces. I know it is not easy to feed that often, but some babies are that way. My 1st nursed every 45-90 mins day & night until he was about 4 months old & I worked - so I get it. It is not safe however to introduce things that are hard on their digestive tract. The whole reason cereal can make a child space out feedings is because it is hard for them to digest & leaves the tummy full longer, precisely for that reason. If she is hungry - then she needs calories & nutrition - not filler. She is NOT "starving" as long as she is fed regularly - she is just needing more intake than other babies & that isn't a bad thing, it is just hard to keep up with. Why do you not think her Dr is right?

Just up the formula intake from 4 to 6, don't put oatmeal in her bottle. It is dangerous.

4oz isn't very much for her age. She might need a couple of ozs more. She's way too young for any cereal or oatmeal. She need more nutrition from formula, not the empty calories from cereal which would give her tummy aches anyway. along with a whole lot of other health problems, both short-term and for life. Should actually wait until 6 months before starting food. That really is a lot safer. At 6 weeks my daughter was up to 6oz, so your daughter being 2 months she might be OK with 6, or she might need more if it doesn't fill her up. Babies all have different growth spurts at different ages.

Edit: after she's had what she'll take, sit her up and burp her, and keep rubbing her back. Once she's done all that and there's no more wind, offer her the rest of the bottle and see if she will take more. It's pretty common to have to burp and give them a rest after about 2/3 the way through a feed. If she's only feeding that much and wanting feeds every 1 1/2 hours round the clock it might be that the formula isn't all that great for her, and so that's all she'll take of it without getting sick. Try a different brand, or a lactose-free one or soy. Some people have said goats or even sheep milk helps but where I live goat's milk is pretty expensive (2 or 3 times as much as other formulas) and I'm skeptical even though she swore it helped. Personally I'd feel safer with soy, or lactose-free.

Don't give up. I can see how this would drive you crazy, but cereal or oatmeal or adding more powder to thicken the formula will just make it worse, not better. She'll just be thirsty after it, and will likely need more feeds if anything. Not to mention anything like that really is dangerous.

I'm afraid you just need to keep feeding her when she wakes. She is too young for anything other than milk. The advice someone else gave about winding her well, then offering her more milk is very good advice. Try that and see if she will take more milk in one feed.

You can buy "hungry baby" milks which some people find helpful, although it has no nutritional benefit, but it would be a better option than starting baby cereal too early.

Mix a very small amount of baby rice cereal with milk, feed to your daughter with a baby spoon and then give formula. Just do this once a day and your baby will be fine.
NEVER NEVER EVER add cereal to a bottle.....baby can choke.
Today's mothers, and doctors, will tell you to wait.........perhaps that works for their babies......
I'm from the 'Old Fashioned' era and was told (by a great honest old fashioned doctor)..'if your baby is hungry - feed it'. Also, from this same doctor, a newborn's digestive system can handle 'gravy consistency' baby rice cereal from day one.....the baby will be fine with no side or after effects. I did this with my first born, when he was just 10-days of age; he is a healthy young man now with NO digestive problems and has NEVER had any weight problems.
If ever in doubt; ask your mother, aunts or grand mothers. They ALL know what works and what doesn't work.