Games like GreenGrass
Games like GreenGrass include Firewatch, What Remains of Edith Finch, The Beginner's Guide, Samsara Room, and FAR: Lone Sails. We matched them by the tags players give GreenGrass on Steam (Adventure, Atmospheric, Singleplayer, Immersive, and Short): closest matches first, and among equally close ones the better-known games.

Firewatch
Shared: Adventure · Atmospheric · Singleplayer

What Remains of Edith Finch
Shared: Atmospheric · Adventure · Walking Simulator

The Beginner's Guide
Shared: Atmospheric · Walking Simulator · Adventure

Samsara Room
Shared: Adventure · Singleplayer · Free to Play

FAR: Lone Sails
Shared: Adventure · Atmospheric · Singleplayer

Brothers - A Tale of Two Sons
Shared: Adventure · Atmospheric · Short

Stray
Shared: Adventure · Atmospheric · Singleplayer

Where Winds Meet
Shared: Singleplayer · Free to Play · Adventure

The Witcher 3: Wild Hunt — Remastered
Shared: Atmospheric · Adventure · Singleplayer

Gone Home
Shared: Atmospheric · Short · Walking Simulator

Little Nightmares
Shared: Adventure · Atmospheric · Singleplayer

POOLS
Shared: Atmospheric · Walking Simulator · Singleplayer

The Room
Shared: Atmospheric · Adventure · Singleplayer

DEATH STRANDING DIRECTOR'S CUT
Shared: Atmospheric · Adventure · Walking Simulator

Fallout 4
Shared: Singleplayer · Adventure · Atmospheric

Resident Evil 7 Biohazard
Shared: VR · Singleplayer · Atmospheric

Hellblade: Senua's Sacrifice
Shared: Atmospheric · Adventure · Singleplayer

Microsoft Flight Simulator (2020) 40th Anniversary Edition
Shared: VR · Singleplayer · Adventure

Scanner Sombre
Shared: Adventure · Atmospheric · Walking Simulator

Half-Life: Alyx
Shared: VR · Singleplayer · Atmospheric

The Long Dark
Shared: Atmospheric · Adventure · Singleplayer

The First Tree
Shared: Adventure · Atmospheric · Walking Simulator

Little Nightmares II
Shared: Adventure · Singleplayer · Atmospheric

The Mr. Rabbit Magic Show
Shared: Adventure · Atmospheric · Singleplayer