The episode, which is entitled "Rule #21: Leave Childishness to Children," will air at 10 PM ET; check local listings.
Peters, who can currently be seen in the new Amazon series "Mozart in the Jungle," will play the mother of Janeane Garofalo's character.
The upcoming episode is described as such: "After the disastrous date with Nate, Abby (Lisa Edelstein) goes on a date with her hot, young pursuer, Will (Warren Christie). Meanwhile, Lyla’s (Janeane Garofalo) mother, Annie (Bernadette Peters), comes to Los Angeles to help her make the best impression possible with the visiting caseworker. Phoebe (Beau Garrett) tells her friends she’s in a polyamorous relationship."