It's not that kind of a feast. Feast days in the church calendar are days of celebration, such as Christmas. Lammastide is one such day. But the play ends long before Lammastide: it is two weeks away in Act 1 Scene 3, and the events of the play take less than a week.
Lord Capulet is hosting the feast of Lammas tide in "Romeo and Juliet." He is Juliet's father and a prominent figure in Verona.
Religious festival around August 1st.
The Capulets throw a big feast in Romeo and Juliet where Romeo and Juliet first meet and fall in love.
Romeo and Juliet first met in a feast at Capulet's house.
Romeo
Juliet recognizes Romeo's voice at the Capulet's feast.
at capulet's ball/feast.
Capulet did.
Romol
Lord Capulet throws a huge feast in "Romeo and Juliet" where Romeo and Juliet first meet each other.
The masquerade party in Romeo and Juliet is hosted by Lord Capulet, Juliet's father. It is held at the Capulet household.
No Montagues were invited, including Romeo. Mercutio was invited, but he's not a Montague.
Romeo's infatuation with Rosaline causes him to crash the Capulet's feast where he first encounters Juliet. That's the best answer I can make from the vague question.