An oven is a piece of technology used for cooking food, prior to consumption.
A "toaster oven" was a type of oven used on Earth in the 20th century. In 1986, a refuse worker complained, to his colleague, about his wife requesting one such oven, but he couldn't afford the sixty dollars required to purchase it. (Star Trek IV: The Voyage Home)
Ovens continued to be used into the 24th century, despite the existence of replicators. In 2367, after crash landing on the desert moon of Lambda Paz, Captain Jean-Luc Picard noted that he and Wesley Crusher should make finding shelter from the sun their first priority, as the shuttle they were on would likely act like an oven in the intense heat. (TNG: "Final Mission")
Neelix used an oven to prepare meals for the crew of the USS Voyager during their time stranded in the Delta Quadrant. In 2373, he prepared some Enaran algae puffs which he offered to Lieutenant Tom Paris and Ensign Harry Kim, "fresh from the oven". (VOY: "Remember")
In 2375, while on a mission to destroy the Monac shipyards, Quark muttered to himself, "Take me out of the oven, Moogie. I'm cooked", in reference to the proximity of the nearby sun. (DS9: "Shadows and Symbols")