Margaret de Quincy was the eldest daughter and co-heiress of Roger de Quincy. She was born before 1223, and inherited a sixth of the barony of Leicester, Leicestershire.
She married William De Ferrers, Fifth Earl of Derby before 1238. Their son, Robert, was born about 1239.
15 Mar 1264: "Protection without clause, until Whitsunday, for Margaret de Ferrariis, countess of Derby." 
William died at Evington, near Leicester, on March 24th or 28th, 1254, and was buried at Merevale Abbey on 31 Mar. 1254.
Banco Roll, Michaelmas, 2—3 E. I.
"Staff. Margaret de Ferrars Countess of Derbeye sued Thomas Meverel to give up to her Agnes, the niece and heir of William Herberd, (fn. 2) whose wardship belongs to her, inasmuch as the said William held his land of her by knight's service." 
Banco Roll, Easter, 8 E. I (1280)
"Leye. and Suff. Philip de Chetewynt appeared against Alexander Comyn Earl of Boghan and Elizabeth his wife in a plea that jointly with Margaret de Ferrars and Elena la Zouche, (fn. 5) they should warrant to him the third part of eight messuages, eighty acres of land, and 20s. of rent in Tudenham near Camham in co. Suffolk, which Roger de Trumpington claimed against him. The defendants did not appear, and are to be re-summoned for the Octaves of St. John the Baptist. m. 17, dorso." 
Monday after the Invention of the Holy Cross, 9 Edw. I.
"413. Margaret de Ferrariis, countess of Derbeye."
"... on the complaint of William de Ferrariis that the sheriff of Essex had taken into the king's hand the manors of Wodeham, Stubbyng and Feirstude which he had demised to the said Margaret, his mother, who had restored them to him long before her death, 15 April, 9 Edw. I."
"... and the issues of the manors were collected by Robert de Duffeld his guardian (custodem) and placed in ward (custodiam) at Tyleteya, and in the fifth year they were rendered to the said William, and so he remained in peaceful seisin until he was made a knight and was of full age. Afterwards he granted these manors, &c. to Lady Margaret de Ferrariis his mother for her life for lands, &c. in Scotland and Gaweye of which she enfeoffed him, and into the aforesaid manors he had ingress sixteen days before his mother's death by her assent." 
Royal Ancestry 2013 Vol. II p. 561-565
Magna Carta Ancestry 2011 2nd ed. Vol. II p. 150-153
↑ Quincy, John. The Big Quincy Book. Chicago, IL: Quincy Publishing, 1914. Page 123.
↑ "Plea Rolls for Staffordshire: 8 Edward I," in Staffordshire Historical Collections, Vol. 6 Part 1, ed. G Wrottesley (London: Staffordshire Record Society, 1885), 102-112. British History Online, accessed March 20, 2017, .
↑ "Inquisitions Post Mortem, Edward I, File 28," in Calendar of Inquisitions Post Mortem: Volume 2, Edward I, ed. J E E S Sharp (London: His Majesty's Stationery Office, 1906), 230-238. British History Online, accessed April 3, 2017, .
For additional information about early baronies, see the top-level category page Early English Feudal Baronies. Individual category pages (links below) should include information specific to the category.
Edited for January 2014 Style Standards. Thank you to everyone who contributed to this profile.