I think I managed to get DD onto cow's milk (after formula) right around the time she turned one... DD isn't fussy though and will take just about anything you put in front of her so maybe your bub is different.
At 12 months, she was having 3 x 300ml bottles of cow's milk, one in the morning upon waking up, one to put her down for her midday nap, and one to put her to bed at night. As the comfort ones tend to be harder to eliminate, I decided to get rid of the morning bottle first, replacing it with 'real' breakfast (usually Weetbix and cow's milk, if your bub likes formula then give Weetbix a go with formula - or you could try it with cow's milk because the taste will be different due to being mixed with cereal) and now at nearly 20 months she is starting to go without her other two bottles if I have given her a full belly and worn her out I find it's easier to replace that morning bottle because they've just woken up and they're in a good mood, happy to accept food over a bottle, but at nap times they can get cranky and stubborn, kwim?

I was told that bottles aren't an essential part of their diet at this age, but again, it's more a comfort/familiar routine thing than a nutritional thing, so just go with what your gut tells you. Of course you can seek advice from your doctor, but every child is different (for instance, when DD was born she was feeding every hour rather than every 3 hours, and eating as much every feed as the 3-hour feed babies were consuming - our midwife told me to flat-out refuse her feeds but the fact is she was just a hungry baby, her advice didn't help), so you will work out what is best for you guys.