Miranda was born in Los Angeles, California on May 14, 1993.When she was about 5 years old she started singing and dancing in "Taste of LA", a restaurant. A talent agent dining at the same restaurant saw potential in her and signed her up for his talent agency, leading to a career in advertising soon after, as well as other roles and shows. She began homeschooling after she finished elementary school, and then enrolled in an online school program which she has been doing since 2006.

The starting point of her career was when she got roles in ads for McDonald's. Later on she auditioned for roles in several movies and TV series. Her audition for the role of a student named Summer Hathaway in the film School of Rock starring Jack Black was successful and she began filming in 2002. School of Rock went on to be a hit. During School of Rock's premiere, news arrived that a pilot for a TV show she participated in had been green-lit, and that she would be playing the part of Megan Parker, the scheming sister of Drake, in the hit kids' show Drake & Josh. She also had a role in the 2005 film Yours, Mine, and Ours. Her character, Joni North, was the sister of Dylan North (Drake Bell), who is her co-star in Drake & Josh. In 2006, she had a minor role in the film Keeping Up with the Steins as Karan Sussman. Also in 2006 a feature-length episode of Drake & Josh called Drake & Josh Go Hollywood had her again playing the role of Megan Parker, and again in the second feature-length episode Drake & Josh: Really Big Shrimp, which aired August 3, 2007. In the same year, production on Drake & Josh had ceased. Cosgrove has also guest starred in a number of Nickelodeon television shows including All That, Zoey 101, Just Jordan and Unfabulous. She plays the role of Carly Shay in the new Nickelodeon series iCarly, that debuted on September 8, 2007. The theme song is performed by Cosgrove, with backup vocals by Drake Bell. Co-starring is Jerry Trainor, who plays Crazy Steve on Drake & Josh.

--Wikipedia