It would be doable with hand luggage - if everything works out and if your Tegel bound flight on EasyJet is not delayed. However if the flight is delayed by more than 20 minutes, it would be tight. And since you are on a separate ticket, British Airways is not liabel in case you miss your flight and have no fully flexible ticket.

I assume you have checked luggage on your Tegel flight as well? Add 30 minutes for waiting of your luggage after your arrive, this cuts the transfer time to 1:30. Now your flight is delayed by 20 minutes than you are down to 1:10, head up to the BA counters and your are approaching luggage check in closing time rapidly.

In short - I would not do this with such a short connection time on separate tickets. I would book with at least the double amount of time between the flights.