On September 22, 2018, he made his Orlando debut against Houston Dynamo as manager James O'Connor continued to assess his options at the position.

[16] After missing the next game through injury, Grinwis came straight back into the team the week after and retained the starting job until the end of the season.

[17] On November 21, 2019, it was announced Grinwis had his contract option for the 2020 season declined by Orlando as part of the end-of-season roster decisions.

[22] With Pedro Gallese on international duty, Brandon Austin recalled by Tottenham at the end of his loan and Mason Stajduhar injured, Grinwis became the fourth goalkeeper to appear, and subsequently win a game, for Orlando City in 2021 after making his second debut for the club on September 4 in a 3–2 victory at home to reigning MLS Cup champions Columbus Crew.

In December 2023, as part of the end of season roster moves, it was announced Grinwis had his option declined and was released as a free agent.