From Buffyfest blog:
After watching the first 3 seasons of Buffy, move on to this order.
This is order is designed for minimum disc switching.
Seasons 4/1
Buffy Season 4 - The Freshman
Angel Season 1 - City of...
Angel Season 1 -Lonely Hearts
Buffy Season 4 - Living Conditions
Buffy Season 4 - The Harsh Light Of Day
Angel Season 1 -IN THE DARK
Angel Season 1 -I FALL TO PIECES
Buffy Season 4 - Fear Itself
Buffy Season 4 - Beer Bad
Buffy Season 4 - Wild at Heart
Buffy Season 4 - The Initiative
Angel Season 1 -RM W/A VU
Angel Season 1 -Sense and Sensitivity
Angel Season 1 -The Bachelor Party
Buffy Season 4 - Pangs
Angel Season 1 -I Will Remember You
Buffy Season 4 - Something Blue
Angel Season 1 -Hero
Angel Season 1 -Parting Gifts
Buffy Season 4 - Hush
Buffy Season 4 – Doomed
Buffy Season 4 - A New Man
Angel Season 1 -Somnambulist
Angel Season 1 -Expecting
Angel Season 1 -She
Buffy Season 4 - The I In Team
Buffy Season 4 - Goodbye Iowa
Angel Season 1 -I've Got You Under My Skin
Angel Season 1 -The Prodigal
Angel Season 1 -The Ring
Angel Season 1 -Eternity
Buffy Season 4 - This Year's Girl (1 of 2)
Buffy Season 4 - Who Are You? (2 of 2)
Buffy Season 4 - Superstar
Buffy Season 4 - Where the Wild Things
Angel -Five by Five (part 1 of 2)
Buffy Season 4 - New Moon Rising
Angel -Sanctuary (part 2 of 2)
Buffy Season 4 - The Yoko Factor
Angel Season 1 -War Zone
Angel Season 1 -Blind Date
Buffy Season 4 - Primeval
Buffy Season 4 - Restless
Angel Season 1 -To Shanshu in LA
Seasons 5/2
Buffy Season 5 Episode 1: Buffy vs. 55