Does the pot have good drainage? And it is not sitting someplace where the plant is getting overly hot and baked in the pot? I know it gets quite warm in Texas. :) Other than that, plants that get moved from indoors (including greenhouses) to outdoors need to be hardened off to outdoors conditions gradually.

FataMorgana

Newtexas,
Are there plenty of drain holes in the pot?
Did you use potting soil, or potting mix. They also
sell Garden soil, go check the bag to see what the bag said.
You only put potting soil or potting mix in a pot.
Is the peppermint getting plenty of sun?
If it's in potting mix, and there are drain holes in the pot, and it is in sunshine alot of the day, just let it dry out.
Ignore it for a few days.
When it asks for water, it fells dry, just water it.
It will be ok.
Let it dry out a bit. Cut off really bad looking parts with sissors, it's going to grow back.

I grow all my mints (peppermint, spearmint, orange mint, chocolate mint, grapefruit mint, candy cane mint, and some others) in pots that stay out in the yard year round (zone 7). They die back in the winter and come back in the spring. I'd probably be concerned if the pot is too small, as the roots grow vigorously, and can become rootbound. With a deep enough pot, I can keep a tray under the big pots so that when I water I fill it up. They can't dry out (as that would kill them), and they don't like to be saturated, so just a good potting mix and only watering when they actually need it should be fine.