Which 2011 game was the last all-new Rhythm Heaven entry before Groove?

The 2011 game that was the last all-new Rhythm Heaven entry before Rhythm Heaven Groove was Rhythm Heaven Fever. It was first released in Japan for the Wii in July 2011, with international versions arriving during 2012.

Rhythm Heaven Fever was the third major game in the series, following the Japan-only Rhythm Tengoku on Game Boy Advance and Rhythm Heaven on Nintendo DS. Its control scheme was built around the Wii Remote's A and B buttons, including actions that required pressing or holding both buttons together. The game also introduced cooperative play for selected rhythm stages.

The wording “all-new” matters because Rhythm Heaven Megamix followed Fever on Nintendo 3DS in 2015, but it was designed largely as a compilation and remix of earlier material, alongside a smaller set of new rhythm games. It is therefore commonly described as the fourth entry, but not the last wholly new installment before Groove.

Rhythm Heaven Groove was announced for Nintendo Switch as the series' next new game after a long gap. That makes Fever the relevant answer, while Rhythm Heaven Megamix is the likely distractor for players thinking only about release order.