Grassland

Spawning data tags simply contain a list of Biomes. If you're referring to this list for a Pokemon, please double-check if it has an Anti Condition or Anti Biome. Anti Conditions and Anti Biomes are a way to essentially state: not in this biome/condition, so you'll need to cross-reference them. For instance, if a Pokemon is set to spawn in is_ocean, but has an anti condition of is_cold, it will not spawn in cold oceans.

Our Pokemon spawns are generally based on default Cobblemon configurations with additions to allow the entire dex to spawn in all Minecraft biomes and supported biome mods. Most biome mods are supported such as Terralith, Oh Biomes You'll Go, Incendium, Better Nether, Gardens of the Dead, and The Bumblezone. Other biome mods may also be compatible, provided they label their biomes with data tags.

Grassland Biomes
minecraft:plains	minecraft:sunflower_plains	minecraft:meadow
minecraft:savanna	minecraft:savanna_plateau	minecraft:windswept_savanna
terralith:brushland	terralith:steppe	terralith:valley_clearing
terralith:alpine_highlands	terralith:arid_highlands	terralith:blooming_plateau
terralith:highlands	terralith:ashen_savanna	terralith:desert_oasis
terralith:fractured_savanna	terralith:hot_shrubland	terralith:red_oasis
terralith:savanna_badlands	terralith:savanna_slopes	terralith:shrubland
byg:allium_fields	byg:amaranth_fields	byg:autumnal_valley
byg:coconino_meadow	byg:prairie	byg:rose_fields
wythers:berry_bog	wythers:cool_forest_edge	wythers:dry_tropical_grassland
wythers:forest_edge	wythers:spring_flower_fields	wythers:subtropical_forest_edge
wythers:tropical_grassland	wythers:bamboo_jungle_highlands	wythers:eucalyptus_deanei_forest
wythers:forested_highlands	wythers:highlands	wythers:huangshan_highlands
wythers:highland_tropical_rainforest	wythers:jade_highlands	wythers:wistman_woods
wythers:granite_canyon	wythers:tropical_forest_canyon	wythers:tropical_forest