V(てform)+おく has two meanings.
① to do something in advance
Ex) 明日はテストなので、復習しておく。
This sentence is saying you have a test tomorrow so you are preparing in advance.
② to leave something
Ex) 部屋が暑いので、エアコンをつけておく。
This sentence is saying you leave your AC keep running because it’s hot.
And your sentence uses おいて which is a request form of ② so it’s saying “there is/are vegetable(s) in the fridge so take it out and leave it.”
Hope it helps!