You will not find an orange included in any ancient Haggadah. It is a brand new tradition and it demonstrates just how quickly new traditions can spread. 

Its origins lie in a fable that some university students invented for a feminist Haggadah in the 1980s. It tells the story of a girl who asks a rabbi about the placein Judaism for a lesbian. The angri rabbi retorts, "There's as much room for a lesbian in Judaism as there is for a crust of bread on the Seder plate."

When a prominent professor of Jewish studies came across the students' Haggadah, it gave her an idea for a new ritual. Placing bread on her Seder plate was out of the question. This, she believed, who suggest that people who were different violated Judaism. But maybe another symbol might do the trick. She selected the orange, noting that "it suggests the fruitfulness for all Jews when lesbians and gay men are contributing and active members of Jewish life."

Today thousands of Jews around the world place an orange on their Seder plate. It serves as a proud statement of inclusivity. 

haggadah Section: Commentary / Readings
Source: Rabbi Jeff Falick