After caretaker manager Nigel Pearson's departure on Tuesday, reserves coach Craig Shakespeare led the Baggies.
But it did not seem to affect them as Gera headed home Nathan Ellington's cross and then Kamara slid home neatly.
Shefki Kuqi missed a gilt-edged chance for Palace, whose fourth home loss of the season led to boos from the fans.
West Brom reserve-team coach Craig Shakespeare on new manager Tony Mowbray:
"He came into the dressing room for an insight. It's a great time for him to come in as the team's flying.
"We won't get carried away. We have to make sure we carry on working hard.
"The players have to apply themselves, and I'm sure Tony will stress that to them. We certainly have the talent."
Crystal Palace: Kiraly, Ward, Hudson (Freedman 46), Cort, Borrowdale, Watson, Kennedy, Fletcher (Green 68), Soares, Scowcroft, Kuqi (Morrison 68).
Subs Not Used: Speroni, Granville.
Booked: Hudson, Scowcroft.
West Brom: Zuberbuhler, Robinson, Perry, Curtis Davies, Albrechtsen, Greening, Gera, Carter, Koumas, Ellington (Quashie 73), Kamara.
Subs Not Used: Steele, Watson, Hartson, McShane.
Booked: Curtis Davies, Perry.
Goals: Gera 45, Kamara 48.
Ref: R Lee (Brentwood).