Caterpillars munch on grasses, including fine-leaved ones such as:
And broad-leaved grasses such as:
Adults take nectar from a range of flowers including:
This butterfly spends the winter as a caterpillar, hiding in dense clumps of grass during the coldest weather but continuing to feed when it is warm enough.
There is even more about this species on the main Butterfly Conservation website
The bright green caterpillars of the Meadow Brown feed on grasses during the day when they are very young, and switch to night-time feeding as they get older. When they’re not feeding, the caterpillars rest, head down, on a grass stem, deep in the vegetation.